Semiconductor memory device

ABSTRACT

A semiconductor memory device includes a first data bus having a first width, and a second data bus which is separate from the first data bus and which has a second width which is different from the first width. The semiconductor memory device further includes a data transfer unit configured for transferring data from memory cells connected to a plurality of bit lines. In a first operational mode, the data transfer unit connects a first number of bit lines from among the plurality of bit lines to the first data bus to transfer the data, the first number being equal to the first width. In a second operational mode, the data transfer unit connects a second number of bit lines from among the plurality of bit lines to the second data bus to transfer the data, the second number being equal to the second width.

CROSS-REFERENCE TO RELATED APPLICATIONS

A claim for priority under 35 U.S.C. §119 is made to JP PatentApplication Nos. 2012-267081 filed Dec. 6, 2012, 2012-269696 filed Dec.10, 2012, and 2013-008915 filed Jan. 22, 2013, in the Japan IntellectualProperty Office, the entire contents of which are hereby incorporated byreference.

BACKGROUND

The inventive concepts described herein relate to electronic devices,and more particularly, to semiconductor memory devices.

Semiconductor memory devices are generally classified as either volatilememory devices or nonvolatile memory devices. Examples of volatilememory in dynamic random access memory (DRAM) and static RAM (SRAM).Examples of nonvolatile memory include electrically erasableprogrammable read only memory (EEPROM), ferroelectric RAM (FRAM),phase-change RAM (PRAM), magnetoresistive (MRAM), and flash memory.Volatile memory devices are characterized by the loss of data storedtherein at a power-off condition, while the nonvolatile memory devicesare characterized by the retention of data stored therein at a power-offcondition.

Among the aforementioned examples of nonvolatile memory, flash memory(which was development from EEPROM technology) has proven to beparticular popular due to its relatively high programming speed, lowpower consumption, and mass storage capacity. As such, flash memory hasbeen widely adopted in the marketplace, and is implemented within amyriad of different types of data storage devices, such as solid statedrives (SSD), SD cards, and memory cards, just to name a few.

SUMMARY

One aspect of embodiments of the inventive concept is directed toprovide a semiconductor memory device which includes a first data bushaving a first width, and a second data bus which is separate from thefirst data bus and which has a second width which is different from thefirst width. The semiconductor memory device further includes a datatransfer unit configured to operate in a first operational mode fortransferring data from memory cells and a second operational mode fortransferring data from the memory cells, where the memory cells areconnected to a plurality of bit lines. In the first operational mode,the data transfer unit connects a first number of bit lines from amongthe plurality of bit lines to the first data bus to transfer the data,the first number being equal to the first width. In the secondoperational mode, the data transfer unit connects a second number of bitlines from among the plurality of bit lines to the second data bus totransfer the data, the second number being equal to the second width.

The first width may be p and the second width may q, where p and q arenatural numbers and p>q, and the plurality of bit lines may be n bitlines, where n is a natural number and a common multiple of p and q.When (n/p) address signals are received, the data transfer unit mayconnect p bit lines to the first data bus in the first operational mode,and when (n/q) address signals are received, the data transfer unit mayconnect q bit lines to the second data bus in the second operationalmode.

The semiconductor memory device may further include a memory array, apage buffer which reads data from the memory array in a page unit andstores the read data, an ECC unit which corrects an error of the readdata provided from the page buffer and writes the corrected data back inthe page buffer, and an interface unit which outputs the read datawritten back in the page buffer. The first data bus may be connected tothe ECC unit and the second data bus may be connected to the interfaceunit. Further, the page buffer may store write data provided to theinterface unit, and the ECC unit may generate parity data on the writedata transferred from the page buffer and write the parity data and thewrite data back in the page buffer. Also, the memory array may be a NANDflash memory cell array.

Another aspect of embodiments of the inventive concept is directed toprovide a semiconductor memory device which includes a first data bushaving a first width, and a second data bus which is separate from thefirst data bus and which has a second width which is different from thefirst width. The semiconductor memory device further includes a datatransfer unit configured to operate in a first operational mode fortransferring data from memory cells and a second operational mode fortransferring data from the memory cells, where the memory cells areconnected to a plurality of bit lines. In the first operational mode,the data transfer unit connects a first number of bit lines from amongthe plurality of bit lines to the first data bus to transfer the data,the first number being equal to the first width. In the secondoperational mode, the data transfer unit connects a second number of bitlines from among the plurality of bit lines to the second data bus totransfer the data, the second number being equal to the second width.The data transfer unit includes a first page buffer which amplifies avoltage of a bit line connected to a normal memory cell and latches theamplified result, a second page buffer which is replaced together with anormal memory cell and a bit line when a normal memory cell or a bitline connected to the first page buffer is defective, and a third pagebuffer which amplifies a voltage of a bit line connected to a paritymemory cell and latches the amplified result. The second data bus isconnected to the first and second page buffers and the first data bus isconnected to the first to third page buffers.

The semiconductor memory device may further include a fourth page bufferwhich is connected to the first data bus and is replaced together with aparity memory cell and a bit line when a parity memory cell or a bitline connected to the first page buffer is defective, a first repaircircuit which is connected to the second data bus and replaces a pagebuffer, associated with a defective memory cell or bit line, of thefirst page buffer with the second page buffer, a second repair circuitwhich is connected to the first data bus and replaces a page buffer,associated with a defective memory cell or bit line, of the third pagebuffer with the fourth page buffer, and an ECC circuit which isconnected to the first data bus and corrects an error of data from thefirst and second page buffers based on data from the third and fourthpage buffers. The semiconductor memory device may still further includesa page buffer control circuit which outputs fixed data as an output of apage buffer, associated with a defective memory cell or bit line, of thefirst page buffer. The page buffer control circuit may not allow a writeoperation from the first data bus when a memory cell or a bit line isdefective.

The first operational mode may be a mode of operation in which inputdata of the ECC circuit is output as output data without repairing on apage buffer, associated with a defective memory cell or bit line, fromamong the first page buffer and the second page buffer used for a repairat the second operational mode.

The first width may be p and the second width may be q, where p and qare natural numbers and p>q, and the plurality of bit lines may be n bitlines, where n is a natural number and a common multiple of p and q.When (n/p) address signals are received, the data transfer unit mayconnect p bit lines to the first data bus in the first operational mode,and when (n/q) address signals are received, the data transfer unit mayconnect q bit lines to the second data bus in the second operationalmode.

Still another aspect of embodiments of the inventive concept is directedto provide a semiconductor memory device which includes a first data bushaving a first width, and a second data bus which is separate from thefirst data bus and which has a second width which is different from thefirst width. The semiconductor memory device further includes a datatransfer unit configured to operate in a first operational mode fortransferring data from memory cells and a second operational mode fortransferring data from the memory cells, where the memory cells areconnected to a plurality of bit lines. In the first operational mode,the data transfer unit connects a first number of bit lines from amongthe plurality of bit lines to the first data bus to transfer the data,the first number being equal to the first width. In the secondoperational mode, the data transfer unit connects a second number of bitlines from among the plurality of bit lines to the second data bus totransfer the data, the second number being equal to the second width.The data transfer unit includes a first page buffer which latches dataof a bit line connected to a normal memory cell; and a second pagebuffer which latches data of a bit line connected to a parity memorycell, and the first data bus and the second data bus are connected tothe first page buffer and the second page buffer. The semiconductormemory device further includes an ECC circuit which is connected to thefirst data bus and corrects an error of output data of the first pagebuffer based on output data of the second page buffer. The firstoperational mode is a mode of operation in which the first page bufferis accessed and is also a mode of operation for execution of ECCprocessing where at a data write operation, the ECC circuit generatesparity data based on output data of the first page buffer and writes theparity data at the second page buffer and, at a data read operation, theECC circuit corrects an error of data of the first page buffer based onparity data of the second page buffer and writes the corrected data backin the first page buffer. The second operational mode is a mode ofoperation in which the ECC processing is not executed and the secondpage buffer is not accessed and the first page buffer is accessed.Further, selection and execution one of the first operational mode andthe second operational mode is electrically switchable.

The second page buffer may be accessed through the second data bus atthe second operational mode.

The semiconductor memory device may further include a mask circuit whichoutputs fixed data instead of data output to an external device throughthe second data bus when the second page buffer is accessed at thesecond operational mode.

The semiconductor memory device may further include a third page bufferwhich is connected to the first and second data buses and is replacedtogether with a normal memory cell and a bit line when a normal memorycell or a bit line connected to the first page buffer is defective, afourth page buffer which is connected to the first and second data busesand is replaced together with a parity memory cell and a bit line when aparity memory cell or a bit line connected to the second page buffer isdefective, a first repair circuit which is connected to the second databus and replaces a page buffer, associated with a defective memory cellor bit line, of the first page buffer with the third page buffer at thesecond operational mode, and a second repair circuit which is connectedto the first data bus and replaces a page buffer, associated with adefective memory cell or bit line, of the second page buffer with thefourth page buffer. At the second operational mode, the first repaircircuit may replace a page buffer, associated with a defective memorycell or bit line, of the second page buffer with the fourth page buffer.Further, the first repair circuit may store a column address indicatinga location of a page buffer to repair a page buffer, associated with adefective memory cell or bit line, of the first page buffer and selectsa page buffer to be replaced by the stored column address, and thesecond repair circuit may store a column address indicating a locationof a page buffer to repair a page buffer, associated with a defectivememory cell or bit line, of the second page buffer and selects a pagebuffer to be replaced by the stored column address. Further, thesemiconductor memory may further include a bit conversion circuit whichconverts a column address that the first repair circuit stores into acolumn address that the second repair circuit stores. The third pagebuffer and the fourth page buffer may be selected by the first repaircircuit and the second repair circuit, based on a switching signalindicating whether the semiconductor memory device operates in eitherone of the first and second operational modes.

The semiconductor memory device may further include a page buffercontrol circuit which outputs fixed data as an output of a page buffer,associated with a defective memory cell or bit line, from among thefirst to fourth page buffers, and the page buffer control circuit maynot allow a write operation from the first data bus when a memory cellor a bit line is defective.

The first width may be p and the second width may be q, where p and qare natural numbers and p>q, and the plurality of bit lines may be n bitlines, where n is a natural number and a common multiple of p and q.When (n/p) address signals are received, the data transfer unit mayconnect p bit lines to the first data bus in the first operational mode,and when (n/q) address signals are received, the data transfer unit mayconnect q bit lines to the second data bus in the second operationalmode.

BRIEF DESCRIPTION OF THE FIGURES

The above and other aspects and features will become apparent from thedetailed description that follows, with reference to the followingfigures, in which like reference numerals refer to like parts throughoutthe various figures unless otherwise specified, and in which:

FIG. 1 is a diagram showing a NAND flash memory according to anembodiment of the inventive concepts;

FIG. 2 is a diagram for reference in describing a data read operationassociated with a page buffer 102, a column coding circuit 103, and acolumn coding circuit 108 shown in FIG. 1;

FIGS. 3A and 3B are diagrams for describing an example of a diagramshowing page buffer (PB) unit shown in FIG. 2;

FIG. 4 is a circuit diagram showing an example of a PB unit shown inFIG. 2;

FIG. 5 is a circuit diagram showing an example of a bit internal circuit50 _(—) i (i being an integer of 0 to 7) shown in FIG. 4;

FIG. 6 is a diagram for describing a data write operation associatedwith a page buffer 102, a column coding circuit 103, and a column codingcircuit 108 shown in FIG. 1;

FIG. 7 is a block diagram showing a general NAND flash memory;

FIG. 8 is a diagram for describing a page buffer unit of a page buffer82 shown in FIG. 7;

FIG. 9 is a circuit diagram showing a conventional page buffer unit;

FIG. 10 is a block diagram schematically illustrating an example of aNAND flash memory including an ECC circuit;

FIG. 11 is a block diagram schematically illustrating another example ofa NAND flash memory including an ECC circuit;

FIG. 12 is a block diagram schematically illustrating a NAND flashmemory according to an embodiment of the inventive concepts;

FIG. 13 is a diagram for describing a data read operation associatedwith a page buffer 102, a column coding circuit 103, and an ECC columncoding circuit 108 shown in FIG. 12;

FIGS. 14A and 14B are diagrams for explaining an example of a PB unitshown in FIG. 13;

FIG. 15 is a circuit diagram showing an example of a PB unit shown inFIG. 13;

FIG. 16 is a circuit diagram showing another example of a PB unit shownin FIG. 13;

FIG. 17 is a circuit diagram showing an example of a bit internalcircuit 50 _(—) i (i being an integer of 0 to 7) shown in FIGS. 15 and16;

FIG. 18 is a diagram for describing a data write operation associatedwith a page buffer 102, a column coding circuit 103, and an ECC columncoding circuit 108 shown in FIG. 12;

FIGS. 19A, 19B and 19C are diagrams for describing an example of pagedatas associated with a page buffer 102 shown in FIG. 12;

FIGS. 20A, 20B, 20C and 20D are flow charts for describing an operationof a page buffer 102 shown in FIG. 12;

FIG. 21 is a block diagram showing a general NAND flash memory;

FIG. 22 is a diagram for describing a page buffer unit of a page buffer82 shown in FIG. 21;

FIG. 23 is a circuit diagram showing a conventional page buffer unit;

FIG. 24 is a block diagram schematically illustrating a NAND flashmemory according to an embodiment of the inventive concepts;

FIG. 25 is a block diagram schematically illustrating an example of arandomizer and ECC circuit 107 shown in FIG. 24;

FIG. 26 is a diagram for describing a data write operation associatedwith a page buffer 102, a column coding circuit 103, and an ECC columncoding circuit 108 shown in FIG. 24;

FIGS. 27A and 27B is a diagram showing an example of a PB unit shown inFIG. 26;

FIG. 28 is a circuit diagram showing an example of a PB unit shown inFIG. 26;

FIG. 29 is a circuit diagram showing another example of a PB unit shownin FIG. 26;

FIG. 30 is a circuit diagram showing a bit internal circuit 50 _(—) i (ibeing an integer of 0 to 7) shown in FIGS. 27 and 28;

FIG. 31 is a diagram for describing a data write operation associatedwith a page buffer 102, a column coding circuit 103, and an ECC columncoding circuit 108 shown in FIG. 24;

FIGS. 32A, 32B and 32C are diagrams for describing a data pageassociated with a page buffer 102 of FIG. 24;

FIGS. 33A, 33B, 33C and 33D are flow charts for describing an operationof a page buffer 102 shown in FIG. 24;

FIGS. 34A and 34B are diagrams for describing another example of pagedata associated with a page buffer 102 shown in FIG. 24;

FIG. 35 is a block diagram schematically illustrating another example ofa NAND flash memory;

FIGS. 36A, 36B and 36C are diagrams for describing a mask control schemeof a NAND flash memory 10 shown in FIG. 35;

FIGS. 37A, 37B and 37C are diagrams for describing a redundancy controlscheme of a NAND flash memory 10 shown in FIG. 35;

FIGS. 38A and 38B are flow charts for describing an address scan controloperation;

FIG. 39 is a timining diagram for further describing an address scancontrol operation;

FIG. 40 is diagram for describing address mapping by a column addressAdd_B;

FIGS. 41A and 41B is a diagram for describing a transfer of storeddefect bit information;

FIG. 42 is a diagram showing a transfer path of defect bit informationfrom a latch circuit 104L of a column repair circuit 104 to a PB 8IOunit according to an embodiment of the inventive concepts;

FIGS. 43A and 43B are diagrams for describing a transfer path of defectbit information from a latch circuit 104L of a column repair circuit 104to a PB 8IO unit according to another embodiment of the inventiveconcepts.

FIG. 44 is a block diagram showing a general NAND flash memory;

FIG. 45 is a diagram for describing a page buffer unit of a page buffer82 shown in FIG. 44;

FIG. 46 is a circuit diagram showing a conventional page buffer unit;

FIG. 47 is a block diagram schematically illustrating a NAND flashmemory including an ECC circuit; and

FIG. 48 is a block diagram schematically illustrating another example ofa NAND flash memory including an ECC circuit.

DETAILED DESCRIPTION

Embodiments will be described in detail with reference to theaccompanying drawings. The inventive concept, however, may be embodiedin various different forms, and should not be construed as being limitedonly to the illustrated embodiments. Rather, these embodiments areprovided as examples so that this disclosure will be thorough andcomplete, and will fully convey the concept of the inventive concept tothose skilled in the art. Accordingly, known processes, elements, andtechniques are not described with respect to some of the embodiments ofthe inventive concept. Unless otherwise noted, like reference numeralsdenote like elements throughout the attached drawings and writtendescription, and thus descriptions will not be repeated. In thedrawings, the sizes and relative sizes of layers and regions may beexaggerated for clarity.

It will be understood that, although the terms “first”, “second”,“third”, etc., may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another region, layer or section. Thus, a firstelement, component, region, layer or section discussed below could betermed a second element, component, region, layer or section withoutdeparting from the teachings of the inventive concept.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concept belongs. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present specification and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

First Embodiment

In a conventional semiconductor memory device, a so-called data busconnecting an I/O pad (e.g., an interface unit) and a memory array isformed of a single bus when seen from a sense amplifier (referred to asa page buffer in a flash memory).

FIG. 7 is a block diagram schematically illustrating a conventionalflash memory device. A NAND flash memory 80 shown in FIG. 7 includes amemory array 101, a page buffer 82, a column coding circuit 83, anaddress control circuit 85, and an I/O pad 106.

The memory array 101 is configured to include a plurality of memory celltransistors. Each of the memory cell transistors stores 1-bit data. Aplurality of memory cell transistors of the memory array 101 connectedto the same word line forms a page. Data is written at and read frommemory cell transistors in a page at the same time.

The page buffer 82 is configured to store data corresponding to a pageof the memory array 101. FIG. 8 is a diagram schematically illustratinga page buffer unit of a page buffer 82. FIG. 9 is a circuit diagram of aconventional page buffer unit.

The page buffer 82 includes a page buffer unit shown in FIG. 8 inplurality. The page buffer unit comprises bit circuits 51_0 a to 51_7 athat are respectively connected to bit lines and store data read frommemory cells through the bit lines or data to be written at memory cellsthrough the bit lines.

A multiplexer 52 _(—) b receives a column address (Sub BL Coding) from acolumn coding circuit 83 shown in FIG. 7 and selects one of the bitcircuits 51_0 a to 51_7 a based on the column address (indicating DIO<i>in FIG. 9). That is, the multiplexer 52 _(—) b connects one of eight bitlines to a PB control circuit 83_1.

The PB control circuit 83_1 (a transfer unit) receives a column address(indicating a selection signal Sel in FIG. 9) from the column codingcircuit 83 shown in FIG. 7 and connects a bit circuit selected by themultiplexer 52 _(—) b to an I/O pad 106 as a peripheral circuit througha data bus.

With the above-described structure, each memory cell transistor in apage is connected to a bit circuit of the page buffer 82 through a bitline. One, selected by a column address, from among the bit lines isconnected to a data bus such that a data writing or reading operation ona memory cell is performed.

Returning to FIG. 7, the column coding circuit 83 receives an addressfrom the address control circuit 85. The column coding circuit 83generates column address signals (Sub BL Coding and Coding shown in FIG.8) based on a column address to select a page buffer unit in the pagebuffer 82 corresponding to the column address. Thereby, data is writtenat a memory cell transistor through the I/O pad 106, the data bus, thebit circuit and the bit line. Also, data read from a memory cell isoutput to the exterior of the I/O pad 106 through the bit line, the bitcircuit and the data bus.

The data bus is a wiring used to input and output data between the pagebuffer 82 and the I/O pad 106 and is formed of 8 or 16 lines.

The I/O pad (an interface unit) 106 is an external terminal for datainput/output between the NAND flash memory 80 and the exterior.

In a NAND flash memory, as a storage characteristic of a memory element(a memory cell transistor) disappears during data preservation due todeterioration of a tunnel oxide film caused by a plurality of writeoperations, an error bit generation rate (an error rate) increases. Inparticular, in the NAND flash memory, an error rate increases inproportion to an increase in storage capacity of a memory cell, that is,scale-down of a fabrication process. For this reason, redundancy data(parity data) of an error correcting code (ECC) is added to data to bewritten, and the redundancy data is together written in a flash memoryas a data stream. During a read operation, data is corrected using theredundancy data of the error correcting code. When an error bit isgenerated, data is corrected. The ECC may be processed outside or insidethe NAND flash memory. In the event that the ECC is processed outsidethe NAND flash memory 80, a memory controller connected through the I/Opad 106 processes the ECC.

Meanwhile, in the event that the ECC is processed inside the NAND flashmemory 80, the NAND flash memory 80 necessitates an error detecting andcorrecting circuit (an ECC unit).

FIG. 10 is a block diagram schematically illustrating a NAND flashmemory including an ECC circuit. In FIG. 10, constituent elements thatare the same as those in FIG. 7 are marked by the same referencenumerals, and a description thereof is thus omitted. A NAND flash memory90 shown in FIG. 10 further comprises an ECC circuit 87 as compared witha NAND flash memory 80 shown in FIG. 7. The ECC circuit 87 is connectedto a data bus.

When data is read from memory cell transistors, the ECC circuit 87sequentially receives data (including normal data and redundancy data)corresponding to a page of memory cell transistors and to be stored inthe page buffer 82 through the data bus, and determines whether an errorexists at each bit, based on the page data. The ECC circuit 87 correctsdata when an error exists, and sequentially writes corrected data ineach bit circuit of the page buffer 82 through the data bus. Afterwards,the address control circuit 85 provides a column address to the columncoding circuit 83, the column coding circuit 83 selects a page bufferunit of the page buffer 82, and the corrected data stored in the pagebuffer 82 is read from the I/O pad 106.

When data is written at memory cell transistors, a page of normal datais provided from the page buffer 82 to the ECC circuit 87 and new datais simultaneously provided to the ECC circuit 87 from the I/O pad 106.Redundancy data is generated based on the page of normal data includingthe new data, the normal data and the redundancy data are written at thepage buffer 82, and data is written at memory cell transistors through awrite (program) operation.

In the NAND flash memory 90, when the ECC is processed, data is notoutput to the exterior using a bus width of the I/O pad 106 at a dataread mode. For this reason, a time necessitates to process the ECC. Toreduce a time taken to process the ECC, such a manner that a bus widthis widened at processing of the ECC may be considered. For example, in apatent reference 1, there is disclosed a semiconductor memory deviceincluding a transfer unit that performs a data transfer between a pagebuffer and an ECC circuit using a first data bus at a first mode ofoperation and performs a data transfer using a part of the first databus at a second mode of operation where the ECC is not processed.

FIG. 11 is a block diagram schematically illustrating another example ofa NAND flash memory including an ECC circuit. FIG. 11 shows a transferunit 17 disclosed in FIG. 3 of the aforementioned patent reference 1. InFIG. 11, modes of operation indicated by arrows are respectivelyreferred to as a first mode of operation and a second mode of operation.For ease of description, page buffers respectively corresponding to 8bits are marked by reference numerals 12_1 to 12_8, respectively. InFIG. 11, a box including a first latch circuit 70, a second latchcircuit 71 (including 71A and 71B), and a third latch circuit 72indicates an 8-bit latch circuit.

Below, an operation of the transfer unit 17 when a data read operationis performed will be described. The transfer unit 17 transfers read datafrom the page buffers 12_1 to 12_8 to latch circuits 71_1 to 70_8through a data bus IO/IOn<63:0> during either one of a first mode ofoperation using an ECC unit 20 and a second mode of operation not usingthe ECC unit 20. Here, the latch circuit 70_1 is connected to the databus IO/IOn<7:0>, the latch circuit 70_2 is connected to the data busIO/IOn<15:8>, the latch circuit 70_3 is connected to the data busIO/IOn<23:16>, and the latch circuit 70_4 is connected to the data busIO/IOn<31:24>. The latch circuit 70_5 is connected to the data busIO/IOn<39:32>, the latch circuit 70_6 is connected to the data busIO/IOn<47:40>, the latch circuit 70_7 is connected to the data busIO/IOn<55:48>, and the latch circuit 70_8 is connected to the data busIO/IOn<63:56>.

At the second mode of operation, a column address is provided to thelatch circuits 70_1 to 70_8 four times such that 64-bit data supplied tothe latch circuits 70_1 to 70_8 is output to an 8-bit data busOUTLLn<7:0> and an 8-bit data bus OUTLLn<15:8>. Here, column addressessupplied four times are called as follows. That is, column addressessupplied to the latch circuit 70_1 to 70_4 is referred to as columnaddresses CA1 to CA4. That is, the column addresses CA1 to CA4 aresequentially supplied to the latch circuit 70_1 to 70_4, so that each of8-bit data stored in the latch circuit 70_1, 8-bit data stored in thelatch circuit 70_2, 8-bit data stored in the latch circuit 70_3, and8-bit data stored in the latch circuit 70_4 is transferred to the latchcircuit 71_B1 through the 8-bit data bus OUTLLn<7:0>.

Also, the column addresses CA1 to CA4 are sequentially supplied to thelatch circuit 70_5 to 70_8, so that each of 8-bit data stored in thelatch circuit 70_5, 8-bit data stored in the latch circuit 70_6, 8-bitdata stored in the latch circuit 70_7, and 8-bit data stored in thelatch circuit 70_8 is transferred to the latch circuit 71B_2 through the8-bit data bus OUTLLn<15:8>.

At the first mode of operation, a bus width is doubled to transfer dataof the latch circuits 70_1 to 70_8 to the ECC unit 20. That is, a databus OUTLLn<23:16> and a data bus OUTLLn<31:24> are installed to besubstantially the same as the data buses OUTLLn<7:0> and OUTLLn<15:8>.

With the above description, at the first mode of operation, the latchcircuits 70_1 to 70_8 transfer stored data to the latch circuits 71A_1to 71A_4 when the column addresses CA1 to CA4 are received. The columnaddresses CA1 and CA3 are first supplied to the latch circuits 70_1 to70_8, and the column addresses CA2 and CA4 are then supplied to thelatch circuits 70_1 to 70_8.

First, when the column addresses CA1 and CA3 are supplied at the sametime, the latch circuits 70_1, 70_3, 70_5, and 70_7 transfer data. Thelatch circuit 70_1 transfers 8-bit data to the data bus OUTLLn<23:16> inresponse to the column address CA1 so as to be transferred to the latchcircuit 71A_3. The latch circuit 70_3 transfers 8-bit data to the databus OUTLLn<7:0> in response to the column address CA3 so as to betransferred to the latch circuit 71A_1. The latch circuit 70_5 transfers8-bit data to the data bus OUTLLn<15:8> in response to the columnaddress CA1 so as to be transferred to the latch circuit 71A_2. Thelatch circuit 70_7 transfers 8-bit data to the data bus OUTLLn<31:24> inresponse to the column address CA3 so as to be transferred to the latchcircuit 71A_4.

When there are simultaneously received the column addresses CA2 and CA4following the column addresses CA1 and CA3, the latch circuits 70_2,70_4, 70_6, and 70_8 transfer data. The latch circuit 70_2 transfers8-bit data to the data bus OUTLLn<23:16> in response to the columnaddress CA2 so as to be transferred to the latch circuit 71A_3. Thelatch circuit 70_4 transfers 8-bit data to the data bus OUTLLn<7:0> inresponse to the column address CA4 so as to be transferred to the latchcircuit 71A_1. The latch circuit 70_6 transfers 8-bit data to the databus OUTLLn<15:8> in response to the column address CA2 so as to betransferred to the latch circuit 71A_1. The latch circuit 70_8 transfers8-bit data to the data bus OUTLLn<31:24> in response to the columnaddress CA4 so as to be transferred to the latch circuit 71A_4.

In the first mode of operation, the transfer unit 17 includes the firstlatch circuit 70 to latch data (e.g., 64-bit data of memory celltransistors) output from the page buffer 12 using the data busIO/IOn<63:0> operating at the second mode of operation. As the number ofcolumn addresses supplied at the second mode of operation is set to betwo times more than the number of column addresses supplied at the firstmode of operation, the transfer unit 17 transfers data to the next-stagelatch circuits 71A_1 to 71A_4 using a part of the data bus used at thesecond mode of operation.

It is possible to output data in high speed by using a data bus for thesecond mode of operation in common and widening a bus width at the firstmode of operation. For this reason, a delay caused to operate a circuit(e.g., the latch circuit 70) for switching the second mode of operation(i.e., a normal mode) and the first mode of operation (i.e., an ECCmode) arises. As described above, at the ECC mode, an address decided toan address of a normal mode is supplied such that data is output to abus the width of which is widened. A high-speed data transfer is delayedby a time needed for processing.

Also, when data is transferred, since an address of data transferred toa data bus is decided using an address of a normal mode, it isimpossible to transfer data of an address selected by a user at the ECCmode. For example, referring to the above description, when all columnaddresses CA1 to CA4 are simultaneously selected, data of IO/IOn<63:32>or IO/IOn<31:0> is not transferred to the ECC circuit at the same time.In a conventional technique, when data is transferred, addresses are notcontrolled independently with respect to two modes of operation. Thatis, freedom on address control is low.

Further, in the event that a design of a NAND flash memory includingsuch an ECC circuit is changed to a design of a NAND flash memory 80(refer to FIG. 7) not including the ECC circuit, a design change is madeto delete a function of the first mode of operation on the latch circuit70 (e.g., to prevent data corresponding to two column addresses frombeing output at the same time). A design change is made such that datacorresponding to two column addresses are prevented from being output atthe same time. This is achieved through a design change of an addresscontrol circuit. In a conventional technique, a part of a data bus isshared with respect to the first mode of operation and the second modeof operation. For this reason, a design is complicated when a designchange is made to delete an ECC function.

The inventive concepts is directed to provide a semiconductor memorydevice including a transfer unit capable of improving freedom on addresscontrol together with a high-speed data transfer when a bus width forthe first mode of operation is widened with respect to a bus width forthe second mode of operation.

A semiconductor memory device of the inventive concepts comprises afirst data bus, a second data bus being different in number from thefirst data bus and independent from the first data bus, and a datatransfer unit. When a data transfer with memory cells is performed atthe first mode of operation, the data transfer unit connects bit lines,being equal in number to the first data bus, from among a plurality ofbit lines to the first data bus to transfer data. When a data transferwith memory cells is performed at the second mode of operation, the datatransfer unit connects bit lines, being equal in number to the seconddata bus, from among a plurality of bit lines to the second data bus totransfer data.

Also, the semiconductor memory device of the inventive concepts includesn bit lines (n being a common multiple of p and q being a naturalnumber, p>q). The first data bus is q, and the second data bus is q. If(n/p) address signals are received at the first mode of operation, thedata transfer unit connects p bit lines to the p first data bus. If(n/q) address signals are received at the second mode of operation, thedata transfer unit connects q bit lines to the second data bus. Althoughthe number n of physical bit lines is not a common multiple of p and q,the remaining may be used as dummy bit lines.

Also, in the semiconductor memory device of the inventive concepts, datais read from a memory array by the page unit, read data read from thememory array is stored in a page buffer, an ECC unit corrects an erroron the read data transferred from the page buffer is corrected, and theerror-corrected data is written back in the page buffer, the read datawritten back in the page buffer is output through an interface unit. Afirst data bus is connected to the ECC unit, and a second data bus isconnected to the interface unit.

The page buffer of the semiconductor memory device according to theinventive concepts stores write data provided through the interfaceunit, and the ECC unit generates parity data on the write datatransferred from the page buffer and writes the parity data and thewrite data back in the page buffer.

The semiconductor memory device of the inventive concepts comprises afirst data bus and a second data bus installed to be independent fromthe first data bus. The second data bus is different from the first databus.

When a data transfer with memory cells is performed at the first mode ofoperation, a data transfer unit connects bit lines, being equal innumber to the first data bus, from among a plurality of bit lines to thefirst data bus to transfer data. When a data transfer with memory cellsis performed at the second mode of operation, the data transfer unitconnects bit lines, being equal in number to the second data bus, fromamong a plurality of bit lines to the second data bus to transfer data.

A data bus connected to an output of the page buffer is preparedindependently for the first mode of operation (i.e., an ECC mode) andthe second mode of operation (i.e., a normal mode). For this reason, inthe event that data is transferred to an ECC circuit at the first modeof operation like the above-described conventional technique, data doesnot pass through an unnecessary circuit. Thus, a data transfer isexecuted in high speed by widening a data width from the second data busto the first data bus.

In the transfer unit, an output of the page buffer is independent from adata bus for the first mode of operation and the second mode ofoperation, and an address supplied for a data transfer at the first modeof operation is independent from an address supplied for a data transferat the second mode of operation. Thus, it is possible to improve freedomon address control and freedom on address mapping. For example, whentransferred at the second mode of operation, portions where normal dataand parity data are respectively stored are physically spaced apart fromeach other, and their column addresses are different from each other.For this reason, at the second mode of operation, normal data is readusing a column address on the normal data, and parity data is read usinga column address on the parity data. However, since data is transferredat the first mode of operation with a bus width being widened, addresscontrol and address mapping are executed such that the normal data andthe parity data are provided to an ECC circuit using one column address.

Also, since a data bus for the first mode of operation and a data busfor the second mode of operation are independent from an output of thepage buffer, it is possible to easily delete an ECC function (i.e., anECC circuit) using the first mode of operation and including the firstdata bus. That is, a design change for deleting the ECC function iseasily made.

FIG. 1 is a block diagram schematically illustrating a NAND flash memoryaccording to an embodiment of the inventive concepts. Referring to FIG.1, a NAND flash memory 10 comprises a memory array 101, a page buffer102, a column coding circuit 103, a column coding circuit 108, anaddress control circuit 85, an I/O pad 106, and an ECC circuit 107. InFIG. 1, constituent elements that are substantially identical to thosein FIGS. 7 and 10 are marked by the same reference numerals, and adescription thereof is thus omitted.

As compared with a NAND flash memory 90 shown in FIG. 10, the NAND flashmemory 10 comprises the column coding circuits 103 and 108 instead of acolumn coding circuit 83. A column address provided to the column codingcircuit 103 is different from a column address provided to the columncoding circuit 108. As will be more fully described, the column codingcircuit 108 connects an output of a page buffer (corresponding to a databus IO/IOn in a conventional technique) to one of an ECC bus (e.g., afirst data bus) and a data bus (e.g., a second data bus) from a portiondirectly connected to the page buffer 102 by outputting a selectionsignal Sel_A or Sel_B to a PB control circuit 60 of the page buffer 102.

In particular, the column coding circuit 108 is provided with a columnaddress Address B from the ECC circuit 107. The column address Address Bis independent from a column address Address A provided to the columncoding circuit 103 from a conventional address control circuit 85. Thecolumn coding circuit 108 outputs the selection signal Sel_B to the PBcontrol circuit 60 and connects an output of the page buffer 102 to theECC bus. Thus, address control is independently executed when an outputof the page buffer 102 is connected to the ECC bus or the data bus.

In a NAND flash memory shown in FIG. 11, a transfer unit 17 connects anoutput of a page buffer to a first latch circuit 70 through a data busIO/IOn. That is, the transfer unit 17 shares a data bus at a first modeof operation and a second mode of operation. The NAND flash memory 10according to the inventive concepts prepares an output of a page bufferindependently from the first and second modes of operation, withoutsharing.

In this case, a path between an output of the page buffer and the ECCcircuit 107 does not include a circuit (e.g., a latch circuit, etc.)influencing a high-speed data transfer. Thus, it is possible toimplement a high-speed data transfer. In the event that a design of theNAND flash memory 10 is changed to a design of a NAND flash memory 80(refer to FIG. 7) not including an ECC circuit, a design change iseasily made by only eliminating the column coding circuit 108, the ECCbus, and the ECC circuit 107.

A page buffer 102 including a transfer unit will be more fully describedwith reference to FIGS. 2 to 5. FIG. 2 is a diagram for reference indescribing a data read operation associated with a page buffer 102, acolumn coding circuit 103, and a column coding circuit 108 shown inFIG. 1. FIGS. 3A and 3B are diagrams schematically illustrating a PB 410unit and a PB unit shown in FIG. 2. FIG. 4 is a circuit diagramschematically illustrating a PB unit. FIG. 5 is a circuit diagramschematically illustrating a bit internal circuit 50 _(—) i (i being aninteger of 0 to 7).

Referring to FIG. 2, a portion corresponding to a page buffer 102, acolumn coding circuit 103, and a column coding circuit 108 shown in FIG.1 has a PB4IO unit that latches four data from four IO lines and readsthe latched data from a first data bus or a second data bus or writesdata on the first or second data bus with respect to four IO lines.

In FIG. 2, there are shown ten PB4 IOs, that is, PB0 IO 0123 (PB 4IOunit) 30_0, PB0 IO 4567 (PB 4IO unit) 30_1, PB1 IO 0123 (PB 4IO unit)30_2, PB1 IO 4567 (PB 4IO unit) 30_3, PB2 IO 0123 (PB 4IO unit) 30_4,PB2 IO 4567 (PB 4IO unit) 30_5, PB3 IO 0123 (PB 4IO unit) 30_6, PB3 IO4567(PB 4IO unit) 30_7, PB4 IO 0123 (PB 4IO unit) 30_8, and PB4 IO 4567(PB 4IO unit) 30_9.

Here, an IO line is an input/output line installed between a multiplexer52 b and a PB control circuit 60 with respect to a PB unit as will bemore fully described below. In exemplary embodiments, the IO line iselectrically connected to any one of eight bit lines through amultiplexer 52 _(—) b and eight bit circuits 51_0 a to 51_7 a. That is,the IO line is a signal line through which memory cell transistor dataor data read from a memory cell transistor is transferred.

Since PB 4IO units shown in FIG. 2 have the same structure, a PB 4IOunit 30_0 shown in FIG. 2 is illustrated in FIG. 3A. The PB 4IO unit30_0 is formed of four PB units 30_00 to 30_03.

When an active level (e.g., a high level) of selection signal Sel_A<0>is provided from a column coding circuit 103, each of the PB units 30_00to 30_03 connects an IO line and a data bus (e.g., a second bus) (aswill be described below, a data bus Data_A<7:0>). In this case, asillustrated in FIG. 3A, four read data bits Data_Out_A<0> toData_Out_A<3> are read from four IO lines onto a data bus Data_A<3:0>.

Also, when an active level (e.g., a high level) of selection signalSel_B<0> is provided from a column coding circuit 108, each of the PBunits 30_00 to 30_03 connects an IO line and an ECC bus (e.g., a firstbus) (as will be described below, a data bus Data_B<19:0>). In thiscase, as illustrated in FIG. 3A, four read data bits Data_Out_A<0> toData_Out_A<3> are read from four IO lines onto a data bus Data_B<3:0>.

Referring to FIG. 3B, each of PB units shown in FIG. 3A comprises eightbit circuits 51_1 a to 51_7 a (configured the same as those in FIG. 8),a multiplexer 52 _(—) b (shown in FIG. 8), and a page buffer (PB)control circuit 60.

Below, a detailed circuit of a PB unit will be more fully described withreference to FIGS. 4 and 5. FIG. 5 shows a circuit of each of bitinternal circuits 50_0 to 50_7 shown in FIG. 4. FIG. 5 shows a datasensing unit and a latch unit at a write operation and a driver unit fordriving a signal line at a read operation. In particular, each of thebit internal circuits 50_0 to 50_7 is implemented using transistors andinverter circuits. In addition, a combination of bit circuits 51_0 a to51_7 a and a multiplexer 52 _(—) b shown in FIG. 3B corresponds to thebit internal circuits 50_0 to 50_7. That is, since a bit internalcircuit is selected by a selection signal DIO, it partially has afunction of a bit circuit and a multiplexer 52 _(—) b. Also, a bitinternal circuit shown in FIG. 5 is the same as a bit internal circuitof a conventional PB unit shown in FIG. 11.

As illustrated in FIG. 5, a bit internal circuit 50 _(—) i (i being aninteger of 0 to 7) is formed of an inverter circuit 511, an invertercircuit 512, a transistor 513, a transistor 514, a transistor 515, atransistor 521, and a transistor 522. Here, the transistors 513, 514,515, 521, and 522 may be an N-channel MOS transistor.

A latch unit of the bit internal circuit 50 _(—) i is formed of theinverter circuits 511 and 512. Here, an input terminal of the inverter511 and an output terminal of the inverter 512 are connected to aconnection node N1, and an output terminal of the inverter 511 and aninput terminal of the inverter 512 are connected to a connection nodeN2. The connection node N1 is connected to a memory cell transistor (notshown) through a bit line. Data that a memory cell transistor storesappears on the connection node N1 as Data_i at a read operation. Datathat is to be stored in a memory cell transistor appears on theconnection node N1 as Data_i at a write operation. For example, when amemory cell transistor stores a low level (data 0), a voltage of Data_ihas a low level. When a memory cell transistor stores a high level (data1), a voltage of Data_i has a high level.

In the bit internal circuit 50 _(—) i, a driver unit is formed of thetransistors 515 and 522. The transistor 522 has a drain connected to aline of a read signal RD, a gate connected to a line of a selectionsignal DIO<i>, and a source connected to a drain of the transistor 515.The transistor 515 has a gate connected to the source of the transistor522, a gate connected to the connection node N2, and a source grounded.Here, the selection signal DIO<i> (i being 0˜7) is Sub BL Coding shownin FIG. 3A. For example, a column coding circuit 103 makes one ofselection signals DIO<7:0> become high based on a 3-bit address signalprovided from an address control circuit 85, or a column decodingcircuit 108 makes one of the selection signals DIO<7:0> become highbased on a 3-bit address signal provided from an ECC circuit 107. Bythis, one of bit internal circuits 50_0 to 50_7 shown in FIG. 4 isselected.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data read operation on a memory cell transistor, alogical level of the read signal RD is equal to that of Data_i. That is,for example, when Data_i is at a high level with the read signal RDbeing pre-charged to a high level, the transistor 515 is turned off, thetransistor 522 is turned on, and the read signal RD retains a highlevel. When Data_i is at a low level, the transistor 515 is turned on,the transistor 522 is turned on, and the bit internal circuit 50 _(—) ichanges the read signal RD from a high level to a low level. A line ofthe read signal RD is connected to a PB control circuit 60 as shown inFIG. 4. At a first mode of operation (e.g., an ECC mode), a line of theread signal RD is connected to an ECC bus (e.g., a first data bus) inresponse to a selection signal Sel_B (a column address signal a columncoding circuit 108 outputs). By this, Data_i of the bit internal circuit50 _(—) i is output on the ECC bus as a data read signal Data_Out_B.

Meanwhile, at a second mode of operation (e.g., a normal mode), a lineof the read signal RD is connected to a data bus (e.g., a second databus) in response to a selection signal Sel_A (a column address signal acolumn coding circuit 103 outputs). By this, Data_i of the bit internalcircuit 50 _(—) i is output on the data bus as a data read signalData_Out_A.

Returning to FIG. 5, the transistors 513, 514, and 521 constitute asensing unit of the bit internal circuit 50 _(—) i. The transistor 513has a drain connected to the connection node N1, a gate connected to aline of a write signal DI, and a source connected to a drain of thetransistor 521. The transistor 514 has a drain connected to theconnection node N2, a gate connected to a line of a write signal nDI,and a source connected to the drain of the transistor 521. Thetransistor 521 has a drain connected to the source of the transistor 513and the source of the transistor 513, a gate connected to a line of aselection signal DIO<i>, and a source grounded.

The lines of the write signals DI and nDI are connected to the PBcontrol circuit 60 as shown in FIG. 4. As will be described below, as adata bus and an ECC bus are connected by the selection signal Sel_B atthe first mode of operation, a data write signal Data_In_B is receivedfrom the ECC bus. By this, the PB control circuit 60 varies one of thewrite signals DI and nDI from a low level to a high level in response toa level of the data write signal Data_In_B. At this time, the other ofthe write signals DI and nDI retains a low level. At the second mode ofoperation, connection to the data bus is performed by the selectionsignal Sel_A, and a data write signal Data_In_A is received from thedata bus. By this, the PB control circuit 60 varies one of the writesignals DI and nDI from a low level to a high level in response to alevel of the data write signal Data_In_A. At this time, the other of thewrite signals DI and nDI retains a low level.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data write operation on a memory cell transistor, aData_i level of the bit internal circuit 50 _(—) i is decided accordingto levels of the write signals DI and nDI. More particular, when one ofa data write signal Data_In_A and a data write signal Data_In_B is at alow level (data 0), the PB control circuit 60 outputs a high level ofwrite signal DI and a low level of write signal nDI. By this, thetransistor 513 is turned on and the transistor 514 is turned off. Atthis time, the connection node N1 is set to a low level and theconnection node N2 is set to a high level, so that Data_i has the samelogical low level (data 0) as that of a data bus.

When the data write signal Data_In_A or the data write signal Data_In_Bis at a high level (data 1), the PB control circuit 60 outputs a lowlevel of write signal DI and a high level of write signal nDI. By this,in the bit internal circuit 50 _(—) i, the transistor 513 is turned offand the transistor 514 is turned on. At this time, the connection nodeN1 is set to a high level and the connection node N2 is set to a lowlevel, so that Data_i has the same logical high level (data 1) as thatof a data bus.

Returning to FIG. 4, the PB control circuit 60 comprises a write unitperforming a data transfer from a data bus to a page buffer and a readunit performing a data transfer from a page buffer to a data bus. Theread unit of the PB control circuit 60 is formed of transistors 61 a and61 b. The transistors 61 a and 61 b may be an NMOS transistor. Thetransistor 61 a has a drain connected to a line of the read signal RD, agate connected to a line of the selection signal Sel_A, and a sourceconnected to a data bus (e.g., a second data bus). The transistor 61 bhas a drain connected to a line of the read signal RD, a gate connectedto a line of the selection signal Sel_B, and a source connected to anECC bus (e.g., a first data bus).

Here, the selection signal Sel_A may be a column address signal that acolumn coding circuit 103 generates in response to address bits, forexample, an address Address A received from an address control circuit85 shown in FIG. 1. The selection signal Sel_B may be a column addresssignal that a column coding circuit 108 generates in response to a partof address bits, for example, an address Address B received from an ECCcircuit 107 shown in FIG. 1.

If a high level of selection signal Sel_B is received from the columncoding circuit 108 at a data read operation of an ECC mode (e.g., afirst mode of operation), the read unit of the PB control circuit 60turns on the transistor 61 b such that a line of the read signal RD isconnected to the ECC bus. By this, data of memory cell transistors(Data_i of a bit internal circuit) stored in the bit internal circuits50_0 to 50_7 are output to the ECC bus as a data read signal Data_Out_B.

If a high level of selection signal Sel_A is received from the columncoding circuit 103 at a data read operation of a normal mode (e.g., asecond mode of operation), the read unit of the PB control circuit 60turns on the transistor 61 a such that a line of the read signal RD isconnected to the data bus. By this, data of memory cell transistorsstored in the bit internal circuits 50_0 to 50_7 are output to the databus as a data read signal Data_Out_A. The write unit of the PB controlcircuit 60, as illustrated in FIG. 4, comprises inverter circuits 62,63, 67, NAND circuits 64 and 65, an OR circuit 66, and switches 68 and69. The inverter circuit 62 is a logical inversion circuit, and has anoutput terminal connected to a line of the write signal DI and an inputterminal connected to an output terminal of the NAND circuit 64. Theinverter circuit 63 is a logical inversion circuit, and has an outputterminal connected to a line of the write signal nDI and an inputterminal connected to an output terminal of the NAND circuit 65.

The NAND circuit 64 is a 3-input 1-output NAND circuit, and has a firstinput terminal connected to a line of a write enable signal fDinEnable,a second input terminal connected to an output terminal of the ORcircuit 66, and a third input terminal connected to an output terminalof the inverter circuit 67. An output terminal of the NAND circuit 64 isconnected to an input terminal of the inverter circuit 62. The NANDcircuit 65 is a 3-input 1-output NAND circuit, and has a first inputterminal connected to a line of the write enable signal fDinEnable, asecond input terminal connected to the output terminal of the OR circuit66, and a third input terminal connected to a first input/outputterminal of the switch 68 and a first input/output terminal of theswitch 69. An output terminal of the NAND circuit 65 is connected to aninput terminal of the inverter circuit 63.

The OR circuit 66 is a 2-input 1-output logic circuit, and has a firstinput terminal connected to a line of the selection signal Sel_B and asecond input terminal connected to a line of the selection signal Sel_A.An output terminal of the OR circuit 66 is connected to the second inputterminal of the NAND circuit 64 and the second input terminal of theNAND circuit 65. The inverter circuit 67 is a logical inversion circuit,and has an input terminal connected to the first input/output terminalof the switch 68 and the first input/output terminal of the switch 69and an output terminal connected to the third input terminal of the NANDgate 64.

The switch 68 is a bidirectional switch, and has the first input/outputterminal connected to the input terminal of the inverter circuit 67 andthe third input terminal of the NAND circuit 65 and a secondinput/output terminal connected to the data bus. The switch 69 is abidirectional switch, and has the first input/output terminal connectedto the input terminal of the inverter circuit 67 and the third inputterminal of the NAND circuit 65 and a second input/output terminalconnected to the ECC bus. In addition, an input of the inverter circuit67 is pulled up by a PMOS transistor such that an input of the invertercircuit 67 is not set to a “don't care” sate when any one of thebidirectional switches is unselected.

With the above-described structure, when the write enable signalfDinEnable is at a high level and the selection signal Sel_B is at ahigh level at a data write operation of the ECC mode (e.g., a first modeof operation), the write unit of the PB control circuit 60 turns on theswitch 69 such that one of the write signals DI and nDI transitions froma low level to a high level in response to a level of the data writesignal Data_In_B received from the ECC bus. More particular, when thedata write signal Data_In_B is at a low level (data 0), the write signalDI transitions to a high level. By this, Data_i of one of the bitinternal circuits 50_0 to 50_7 goes to a low level. Afterwards, data 0is written at a memory cell transistor through a program operation.

Meanwhile, when the data write signal Data_In_B is at a high level (data1), the write signal nDI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a high level.Afterwards, data 1 is written at a memory cell transistor through aprogram operation.

If the write enable signal fDinEnable and the selection signal Sel_A goto a high level at a data write operation of a normal mode (e.g., asecond mode of operation), the write unit of the PB control circuit 60turns on the switch 68 such that one of the write signals DI and nDItransitions from a low level to a high level in response to a level ofthe data write signal Data_In_A received from the data bus. Moreparticular, when the data write signal Data_In_A is at a low level (data0), the write signal DI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a low level.Afterwards, data 0 is written at a memory cell transistor through aprogram operation.

Meanwhile, when the data write signal Data_In_A is at a high level (data1), the write signal nDI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a high level.Afterwards, data 1 is written at a memory cell transistor through aprogram operation.

As described above, the PB control circuit 60 is a circuit that controlsa data transfer between a data bus (a first data bus and a second databus) and a memory cell transistor connected through a bit line to one,selected by the selection signal DIO<i>, from among the bit internalcircuits 50_0 to 50_7 constituting a PB unit of a page buffer 102. Theline of the read signal RD, the line of the write signal DI, and theline (IO line) of the write signal nDI are lines connecting the PBcontrol circuit 60 and the bit internal circuits 50_0 to 50_7constituting the PB unit, and are input/output lines for a data transferof the PB unit.

In exemplary embodiments, the PB control circuit 60 transfers write dataand read data between an input/output unit of the page buffer 102 andthe first and second data buses (e.g., the ECC bus and the data bus).Returning to FIG. 3A, by the above-described PB control circuit 60, a PB4IO unit 30_0 operates as follows. when a high level of selection signalSel_A<0> is received from the column coding circuit 103, the PB 4IO unit30_0 connects input/output lines IO_0 to IO_3 (marked by RD) of fourpage buffers to a 4-bit data bus Data_A<3:0>. By this, the PB 4IO unit30_0 outputs the data read signals Data_Out_A<3> to Data_Out_A<0>(hereinafter, referred to as data read signals Data_Out_A<3:0>) on thedata bus Data_A<3:0>.

When a high level of selection signal Sel_B<0> is received from thecolumn coding circuit 108, the PB 4IO unit 30_0 connects input/outputlines IO_0 to IO_3 of four page buffers to a 4-bit ECC bus Data_B<3:0>(here, referred to as data bus Data_B<3:0>). By this, the PB 4IO unit30_0 outputs the data read signals Data_Out_B<3> to Data_Out_B<0>(hereinafter, referred to as data read signals Data_Out_B<3:0>) on thedata bus Data_B<3:0>.

Returning to FIG. 2, by the above-described PB 4IO unit 30_0, a pagebuffer 102 and column coding circuits 103 and 108 (here, referred to asa data read model) operate as follows at a data read operation. also,input/output lines (e.g., data read lines RD shown in FIG. 4) of pagebuffers connected to PB 4IO units 30_1 to 30_9 shown in FIG. 2 arereferred to as IO lines IO_4 to IO_7, IO lines IO_8 to IO_11, IO linesIO_12 to IO_15, IO lines IO_16 to IO_19, IO lines IO_20 to IO_23, IOlines IO_24 to IO_27, IO lines IO_28 to IO_31, IO lines IO_32 to IO_35,and IO lines IO_36 to IO_39. Also, the data bus has an 8-bit bus width,and is referred to as a data bus Data_A<7:0>. The ECC bus has a 20-bitbus width, and is referred to as a data bus Data_B<19:0>.

At the normal mode (e.g., the second mode of operation), the columncoding circuit 103 sets one of column addresses of selection signalsSel_A<0> to Sel_A<4> to a high level and the remaining thereof to a lowlevel and then the selection signals Sel_A<0> to Sel_A<4> to the dataread model. For example, at the normal mode, 40-bit data of the IO linesIO_0 to IO_39 is sequentially output onto the data bus Data_A<7:0> bysequentially providing the selection signals Sel_A<0> to Sel_A<4> to thedata read model.

When the selection Sel_A<0> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0 and the PB 4IO unit 30_1 connect the IO lines IO_0 to IO_7 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_0 and the PB 4IO unit30_1 output read data Data_Out_A<7:0> (data on the IO lines IO_0 toIO_7) on the data bus Data_A<7:0>.

When the selection Sel_A<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_2 and the PB 4IO unit 30_3 connect the IO lines IO_8 to IO_15 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_2 and the PB 4IO unit30_3 output read data Data_Out_A<7:0> (data on the IO lines IO_8 toIO_15) on the data bus Data_A<7:0>.

When the selection Sel_A<2> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_4 and the PB 4IO unit 30_5 connect the IO lines IO_16 to IO_23 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_4 and the PB 4IO unit30_5 output read data Data_Out_A<7:0> (data on the IO lines IO_16 toIO_23) on the data bus Data_A<7:0>.

When the selection Sel_A<3> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_6 and the PB 4IO unit 30_7 connect the IO lines IO_24 to IO_31 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_6 and the PB 4IO unit30_7 output read data Data_Out_A<7:0> (data on the IO lines IO_24 toIO_31) on the data bus Data_A<7:0>.

Finally, when the selection Sel_A<4> goes to a high level, thetransistor 61 a of the PB control circuit 60 is turned on. At this time,the PB 4IO unit 30_8 and the PB 4IO unit 30_9 connect the IO lines IO_32to IO_39 to the data bus Data_A<7:0>. By this, the PB 4IO unit 30_8 andthe PB 4IO unit 30_9 output read data Data_Out_A<7:0> (data on the IOlines IO_32 to IO_39) on the data bus Data_A<7:0>.

As described above, if the selection signal Sel_A is provided to thedata read model five times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_A<7:0> by the 8-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on the databus through bit lines and IO lines IO_0 to IO_39.

At the ECC mode (e.g., the first mode of operation), the ECC circuit 107sets one of column addresses of the selection signals Sel_B<0> andSel_B<1> to a high level and the other to a low level and outputs themto the data read model. 40-bit data of the IO lines IO_0 to IO_39 issequentially read on a data bus Data_B<19:0> by sequentially providingthe selection signals Sel_B<0> and Sel_B<1> to the data read mode.

When the selection Sel_B<0> goes to a high level, the transistor 61 b ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0, 30_2, 30_4, 30_6, and 30_8 connect the data bus Data_B<19:0> to IOlines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, andIO_32 to IO_35. By this, the PB 4IO unit 30_0, 30_2, 30_4, 30_6, and30_8 output read data Data_Out_B<19:0> (data on the IO lines IO_0 toIO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32 to IO_35)on the data bus Data_B<19:0>.

When the selection Sel_B<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_1, 30_3, 30_5, 30_7, and 30_9 connect the data bus Data_B<19:0> to IOlines IO_4 to IO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, andIO_36 to IO_39. By this, the PB 4IO unit 30_1, 30_3, 30_5, 30_7, and30_9 output read data Data_Out_B<19:0> (data on the IO lines IO_4 toIO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, and IO_36 toIO_39) on the data bus Data_B<19:0>.

As described above, if the selection signal Sel_B is provided to thedata read model two times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_B<19:0> by the 20-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on the ECCbus through bit lines and IO lines IO_0 to IO_39. For example, when aselection signal is not provided five times at the normal mode, data onIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not read on the data bus. If a selection signal(e.g., Sel_B<0>) is provided once at the ECC mode, data of the IO linesIO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32to IO_35 may be read out on the ECC bus.

FIG. 6 is a diagram for describing a data write operation of a portioncorresponding to a page buffer 102 and column coding circuits 103 and108 shown in FIG. 1. A data write operation of a page buffer 102 andcolumn coding circuits 103 and 108 (here, referred to as a data writemodel) is performed by an operation of a PB 4IO unit 30_0. A datatransfer of the data write model is performed in a direction opposite toa direction shown in FIG. 2, and a description thereof is thus omitted.

In the data write model, for example, at a normal mode, data provided toIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not written from a data bus when a selectionsignal is not provided five times. In this behalf, if a selection signal(e.g., Sel_B<0>) is provided once at the ECC mode, the remaining data iswritten on the IO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19,IO_24 to IO_27, and IO_32 to IO_35 from the ECC bus.

A semiconductor memory device (or, a semiconductor memory device) 10 ofthe inventive concepts comprises a first data bus Data_B<19:0>, a seconddata bus Data_A<7:0> being different in number from the first data busand independent from the first data bus Data_B<19:0>, and a datatransfer unit (e.g., a PB control circuit 60 of each of PB 4IO units30_0 to 30_9). When a data transfer with memory cells is performed atthe first mode of operation, the data transfer unit connects bit lines,being equal in number to the first data bus, from among a plurality ofbit lines to the first data bus to transfer data. When a data transferwith memory cells is performed at the second mode of operation, the datatransfer unit connects bit lines, being equal in number to the seconddata bus, from among a plurality of bit lines to the second data bus totransfer data.

If the number of bit lines is n (n being a common multiple of p and qbeing a natural number, p>q), the first data bus is q, and the seconddata bus is q. If (n/p) address signals are received at the first modeof operation, the data transfer unit connects p bit lines to the p firstdata bus. If (n/q) address signals are received at the second mode ofoperation, the data transfer unit connects q bit lines to the seconddata bus. Although the number n of physical bit lines is not a commonmultiple of p and q, the remaining may be used as dummy bit lines.

Also, the NAND flash memory 10 comprises a memory array 101, a pagebuffer 82 configured to read data from the memory array 101 by the pageunit and to store read data read from the memory array 101, an ECCcircuit 107 configured to correct an error on the read data transferredfrom the page buffer 82 and to write the error-corrected data back inthe page buffer 82, and an IO pad (or, an interface unit) 106 configuredto output the read data written back in the page buffer 82. An ECC busis connected to the ECC circuit 107, and a data bus is connected to theIO pad 106.

In the NAND flash memory 10, the page buffer 82 stores write datareceived through the IO pad 106, and the ECC circuit 107 generatesparity data on the write data transferred from the page buffer 82. Theparity data and write data are written back in the page buffer.

By this, it is possible to control column coding, that is, addressesindependently by preparing a plurality of data buses (e.g., the ECC busand the data bus). In exemplary embodiments, it is possible to controladdresses independently by forming a data bus to be independent frominput/output lines of the page buffer 102 (e.g., IO_0 to IO_39), thatis, a portion directly connected to the page buffer. Thus, thesemiconductor memory device according to an embodiment of the inventiveconcepts obtains the following effects.

(1) A high-speed operation is implemented by widening a bus width at thefirst mode of operation (e.g., the ECC mode). There is described such acase that when a column address is received once, 8-bit data istransferred to DataBus at the second mode of operation (e.g., the normalmode) and 20-bit data is transferred at the ECC mode. A bus width iseasily widened according to an input of Address_B, that is, columncoding to the page buffer 102. For example, if two column addresses areused for 1024 PB units, it is possible to transfer data with the ECCBusbeing widened a 512-bit bus width at the ECC mode. Also, it is possibleto form a data bus independent from a portion directly connected to thepage buffer and to control addresses independently. For this reason, ascompared with the case that data is transferred to an ECC circuit usinga part of the data bus like a conventional technique, a high-speed datatransfer is implemented. The reason is that there is not required acircuit (e.g., a first latch circuit 70 of a conventional example)associated with address control for separating a data transfer at thenormal mode and a data transfer at the ECC mode.

(2) Freedom on address control and mapping is improved. At a normalmode, when 8-bit data is transferred using a column address, forexample, data of IO lines IO_0 to IO_7 is transferred to DataBus byproviding a selection signal Sel_A<0> to PB 4IO units 30_0 and 30_1. Inthis behalf, at an ECC mode, data on all addresses is transferred to theECC circuit in a lump by allocating an address independent from theselection signals Sel_B<0> and Sel_B<1> to the PB 4IO units 30_0 and30_1. For example, although normal data and parity data are assigned todifferent addresses of the selection signal Sel_A at a normal mode, theyare assigned to the same address of the selection signal Sel_B at theECC mode, and normal data and parity data are transferred to the ECCcircuit in a lump. Thus, address control at the second mode of operationand address control at the first mode of operation are independent fromeach other, and freedom of address mapping is high.

Also, at the normal mode, a column address is used with respect to fiveselection signals Sel_A<0> to Sel_A<4>. At the ECC mode, a columnaddress is used with respect to two selection signals Sel_B<0> andSel_B<1>. This means that although a column address has a value notbeing 2n in case of the user specification of the normal mode, it iseasy to change an address space of the ECC mode to a unit space having avalue of 2n. By this, a code composition of the ECC circuit 107, forexample, a code length (e.g., optimization on code length composition incase of cumulative coding) may be decided with freedom, and optimalperformance is achieved.

(3) A design change is easily made.

In case of designing a product including an ECC circuit, it is assumedthat a product is a derivation product and a product not including anECC circuit is separately designed. In this case, data buses and columncoding circuits associated with address control are independent withrespect to the ECC mode and the normal mode. By this, it is possible toseparate a circuit associated with the ECC mode and a circuit associatedwith the normal mode. Thus, it is easy to eliminate the circuitassociated with the ECC mode. This means that a design change is easilymade.

In the event that a bus width is widened from the second mode ofoperation to the first mode of operation, a high-speed data transfer isachieved, so that the freedom on address control is improved.

A semiconductor memory device of the inventive concepts comprises afirst data bus Data_B<19:0>, a second data bus Data_A<7:0> beingdifferent in number from the first data bus and independent from thefirst data bus Data_B<19:0>, and a data transfer unit (e.g., PB 4IOunits 30_0 to 30_9). When a data transfer with memory cells is performedat the first mode of operation, the data transfer unit connects bitlines, being equal in number to the first data bus, from among aplurality of bit lines to the first data bus to transfer data. When adata transfer with memory cells is performed at the second mode ofoperation, the data transfer unit connects bit lines, being equal innumber to the second data bus, from among a plurality of bit lines tothe second data bus to transfer data.

Second Embodiment

In a conventional NAND flash memory, as a storage characteristic of amemory element (a memory cell transistor) disappears during datapreservation due to deterioration of a tunnel oxide film caused by aplurality of write operations, an error bit generation rate (an errorrate) increases. In particular, in the NAND flash memory, an error rateincreases in proportion to an increase in storage capacity of a memorycell, that is, scale-down of a fabrication process. For this reason,redundancy data (parity data) of an error correcting code (ECC) is addedto data to be written, and the redundancy data is together written in aflash memory as a data stream. During a read operation, data iscorrected using the redundancy data of the error correcting code. Whenan error bit is generated, data is corrected. A semiconductor memorydevice including an ECC circuit for ECC processing is disclosed in apatent reference 1, for example.

In the NAND flash memory, after fabrication, there are tested such a bitbadness that data is not stored in a memory cell transistor, such abadness that a bit line connected to a memory cell transistor isconnected with another bit line, or such a badness that a bit line isopened. In this case, data of a memory cell transistor is latched andamplified through a bit line, and the amplified data is output to theexterior. Or, a set including a page buffer for writing data at a memorycell, a bit line connected to the page buffer and a memory celltransistor connected to the bit line may be replaced with a normal set.This replacement is referred to as a redundancy technique. In asemiconductor memory device, an error bit is using ECC processingwithout replacing an error using the redundancy technique. With such atechnique, however, an error correction capacity of the ECC processingrepairing a memory cell transistor the data storage characteristic ofwhich disappears due to deterioration is consumed when an error bit dueto a fabrication process is repaired. For this reason, the errorcorrection capacity of the ECC processing is lowered.

At present, repair processing of error bits and error correctionprocessing using ECC processing are made independently as will bedescribed below. FIG. 21 is a block diagram schematically illustrating aconventional NAND flash memory. In a NAND flash memory 80 shown in FIG.21, ECC processing is executed by a NAND controller 90 (or, a memorycontroller) placed outside the NAND flash memory 80. The NAND flashmemory 80 shown in FIG. 21 comprises a memory array 101, a page buffer82, a column coding circuit 83, a column repair multiplexer(hereinafter, referred to as a column repair circuit) 84, and an I/O pad106. The NAND controller 90 comprises an ECC engine (or, an ECC circuit)87 and an I/O pad 106 c.

The memory array 101 is configured to include a plurality of memory celltransistors. Each of the memory cell transistors stores 1-bit data. Aplurality of memory cell transistors of the memory array 101 connectedto the same word line forms a page. Data is written at and read frommemory cell transistors in a page at the same time.

The page buffer 82 is configured to store data corresponding to a pageof the memory array 101. FIG. 22 is a diagram schematically illustratinga page buffer unit of a page buffer 82. FIG. 23 is a circuit diagram ofa conventional page buffer unit. The page buffer 82 includes a pagebuffer unit shown in FIG. 22 in plurality. The page buffer unitcomprises bit circuits 51_0 a to 51_7 a that are respectively connectedto bit lines and store data read from memory cells through the bit linesor data to be written at memory cells through the bit lines.

A multiplexer 52 _(—) b receives a column address (Sub BL Coding) from acolumn coding circuit 83 shown in FIG. 21 and selects one of the bitcircuits 51_0 a to 51_7 a based on the column address (indicating DIO<i>in FIG. 23). That is, the multiplexer 52 _(—) b connects one of eightbit lines to a PB control circuit 83_1.

The PB control circuit 83_1 receives a column address Coding (indicatinga selection signal Sel in FIG. 23) from the column coding circuit 83shown in FIG. 22 and connects a bit circuit selected by the multiplexer52 _(—) b to a peripheral circuit through a data bus DataBus_(—)1.

With the above-described structure, each memory cell transistor in apage is connected to a bit circuit of the page buffer 82 through a bitline. One, selected by a column address, from among the bit lines isconnected to the data bus such that data is written at or read from amemory cell.

Returning to FIG. 21, the column coding circuit 83 generates columnaddress signals (Sub BL Coding and Coding shown in FIG. 22) based on acolumn address received from an address control circuit (not shown). Thecolumn coding circuit 83 selects a page buffer unit in the page buffer82 corresponding to the column address. Thereby, data is written at amemory cell transistor through the I/O pad 106, data buses DataBus_(—)2and DataBus_(—)1, the bit circuit and the bit line. Also, data read froma memory cell is output to the exterior of the I/O pad 106 through thebit line, the bit circuit and the data buses DataBus_(—)2 andDataBus_(—)1.

Also, the page buffer 82 comprises PB (Page Buffer)_Data (hereinafter,referred to as a page buffer 82 a) and PB_CR (hereinafter, referred toas a page buffer 82 b). The page buffer 82 a is a page buffer (e.g., afirst page buffer) that amplifies a voltage of a bit line connected to anormal memory cell and latches the amplified result. In the event that anormal memory cell or a bit line connected to the page buffer 82 a isabnormal, the page buffer 82 b is a page buffer (e.g., a second pagebuffer) that is replaced together with a normal memory cell and a bitline. That is, in the event that one of page buffer units constitutingthe page buffer 82 a is abnormal, the abnormal page buffer unit isrepaired with one of page buffer units in the page buffer 82 b.

The column repair circuit 84 is a circuit that repairs an abnormal pagebuffer unit with a page buffer unit of the page buffer 82 b. Forexample, when a column address indicating a location of an abnormal pagebuffer is received at a data read operation on a memory cell transistor,the column repair circuit 84 controls the column coding circuit 83 suchthat a page buffer unit of the page buffer 82 b is selected instead ofthe abnormal page buffer unit of the page buffer 82 a. By this, datafrom a selected page buffer unit is read out to the exterior through thedata buses DataBus_(—)1 and DataBus_(—)2 and the I/O pad 106.

A column address indicating a location of an abnormal page buffer isincluded in repair information shown in FIG. 21. The repair informationis detected by the semiconductor test equipment (e.g., a memory tester)through a test operation executed after fabrication of the NAND flashmemory 80. Afterwards, the detected repair information is stored in astorage area for system of the memory array 101 before shipment, forexample.

Meanwhile, when a column address indicating a location of an abnormalpage buffer is received for a data write operation on a memory celltransistor, the column repair circuit 84 controls the column codingcircuit 83 such that a page buffer unit of the page buffer 82 b isselected instead of the abnormal page buffer unit of the page buffer 82a. By this, data received from the I/O pad 106 is provided to a pagebuffer unit of the page buffer 82 b through the data buses DataBus_(—)2and DataBus_(—)1, not a page buffer unit of the abnormal page bufferunit.

The data buses DataBus_(—)1 and DataBus_(—)2 are lines through whichdata is transferred between the page buffer 82 and the I/O pad 106. Eachof the data buses DataBus_(—)1 and DataBus_(—)2 are normally formed of 8or 16 lines. The I/O pad (or, an interface unit) 106 are externalterminals for data input/output between the NAND flash memory 80 and theNAND controller 90.

The I/O pad (or, an interface unit) 106 c of the NAND controller 90 areexternal terminals for data input/output between the NAND flash memory80 and the NAND controller 90. At a data read operation of the NANDflash memory 80, the ECC engine (or, an ECC circuit) 87 receives dataprovided from the NAND flash memory 80 through the I/O pad 106 c. Thedata provided from the NAND flash memory 80 may be repaired data, butmay include an error. The ECC circuit 87 performs ECC processing (or,decoding processing) on the received data based on own parity data, andoutputs the error-corrected data (e.g., clear data) to the exterior. Ata data write operation of the NAND flash memory 80, the ECC circuit 87generates data received from the exterior and a page of data of the NANDflash memory 80 at which the received data is written, or parity data.The ECC circuit 87 internally stores the parity data, and outputs thewrite data to the NAND flash memory 80 through the I/O pad 106 c.

As described above, since ECC processing is executed outside aconventional NAND flash memory, data when ECC processing is executed isdata passing through the column repair circuit 84, that is, data afteran abnormal column is repaired. However, since the NAND flash memory 80does not transfer data to the exterior using a bus width of the I/O pad106 at ECC processing, that a time for ECC processing is required isproblematic. A manner of widening a bus width at ECC processing may beconsidered to shorten a time for the ECC processing. For example, a buswidth of DataBus_(—)1 and DataBus_(—)2 of the NAND flash memory 80 maybe considered.

However, if a bus width is doubled, to constantly maintain the repairefficiency on erroneous bits, the number of erroneous bits once providedto the column repair circuit 84 for repair may increase two times ascompared with that before a bus width is widened. Thus, the size of thecolumn repair circuit 84 may be doubled. Also, a circuit size of the I/Opad 106 increases. For example, the number of pads increases. In theevent that a bus width is widened for high-speed ECC processing, a chipsize increases to repair erroneous bits.

Also, the NAND flash memory 80 is configured to include the ECC circuit87 for ECC processing. For example, a semiconductor memory device isconfigured such that the NAND flash memory 80 and the NAND controller 90shown in FIG. 21 are integrated in a single chip, the I/O pads 106 and106 c are eliminated, and a portion for outputting clear data is formedof an I/O pad. In this case, however, if a bus width is widened forhigh-speed ECC processing, a chip size increases to repair erroneousbits as described above.

In addition, since data provided to the ECC circuit 87 is data aftererroneous bit repairing, that is, data passing through the column repaircircuit 84, a time for ECC processing becomes longer by a time taken torepair erroneous bits through the column repair circuit.

An object of the inventive concepts is directed to provide asemiconductor memory device that prevents an increase in a size of arepair circuit for replacing an abnormal page buffer associated withabnormal memory cells or bit lines with a normal page buffer andimplements a high-speed data transfer to an ECC circuit.

A semiconductor memory device of the inventive concepts comprises afirst data bus, a second data bus being different in number from thefirst data bus and independent from the first data bus, and a datatransfer unit. When a data transfer with memory cells is performed at anECC mode (e.g., a first mode of operation), the data transfer unitconnects bit lines, being equal in number to the first data bus, fromamong a plurality of bit lines to the first data bus to transfer data.When a data transfer with memory cells is performed at a normal mode(e.g., a second mode of operation), the data transfer unit connects bitlines, being equal in number to the second data bus, from among aplurality of bit lines to the second data bus to transfer data. Also,the data transfer unit comprises a first page buffer that amplifies avoltage of a bit line connected to a normal memory cell and latches theamplified result, a second page buffer that is replaced together with anormal memory cell and a bit line when the normal memory cell or the bitline connected to the first page buffer is defective, and a third pagebuffer that amplifies a voltage of a bit line connected to a paritymemory cell and latches the amplified result. Also, the second data busis connected to the first and second page buffers, and the first databus is connected to the first to third page buffers.

Also, the semiconductor memory device comprises a fourth page bufferthat is replaced together with a parity memory cell and a bit line whenthe parity memory cell or the bit line connected to the third pagebuffer is defective, a first repair circuit that is connected to thesecond bus and repairs a page buffer, connected to a defective memorycell or bit line, from among the first page buffer with the second pagebuffer, a second repair circuit that is connected to the first bus andrepairs a page buffer, connected to a defective memory cell or bit line,from among the third page buffer with the fourth page buffer, and an ECCcircuit that is connected to the first data bus and corrects an error ofoutput data of the first and second page buffers based on output data ofthe third and fourth page buffers.

Also, the semiconductor memory device comprises a PB control circuit 60that sets an output of a page, connected to a defective memory cell orbit line, from among the first page buffer, to fixed data.

Also, when a memory cell or a bit line is defective, the PB controlcircuit does not allow writing from the first data bus.

Also, in a semiconductor memory device of the inventive concepts, duringthe first mode of operation, it is viewed as input data of the ECCcircuit without a repair of a page buffer, corresponding to a defectivememory cell or bit line, from among the first page buffer and the secondpage buffer existing for a repair at the second mode of operation.

Also, the semiconductor memory device of the inventive concepts includesn bit lines (n being a common multiple of p and q being a naturalnumber, p>q). The first data bus is q, and the second data bus is q. If(n/p) address signals are received at the first mode of operation, adata transfer unit connects p bit lines to the p first data bus. If(n/q) address signals are received at the second mode of operation, thedata transfer unit connects q bit lines to the second data bus. Althoughthe number n of physical bit lines is not a common multiple of p and q,the remaining may be used as dummy bit lines.

The semiconductor memory device of the inventive concepts comprises afirst data bus, a second data bus being different in number from thefirst data bus and independent from the first data bus, and a datatransfer unit. When a data transfer with memory cells is performed atthe first mode of operation, the data transfer unit connects bit lines,being equal in number to the first data bus, from among a plurality ofbit lines to the first data bus to transfer data. When a data transferwith memory cells is performed at the second mode of operation, the datatransfer unit connects bit lines, being equal in number to the seconddata bus, from among a plurality of bit lines to the second data bus totransfer data.

By this, a data bus connected to an output of the page buffer isprepared and used independently for the first mode of operation (e.g.,an ECC mode) and the second mode of operation (e.g., a normal mode). Asemiconductor memory device including an ECC circuit has a redundancyfunction for repairing a bad column. But, error correction isimplemented by including data of the bad column and repaired data innormal data and transferring the normal data and parity data to the ECCcircuit using the first mode of operation with a bus width beingwidened. For this reason, a circuit (e.g., a column repair circuit)repairing erroneous bits need not be placed between the ECC circuit andan output of the page buffer. By this, in the event that data istransferred to the ECC circuit with a bus width being widened at thefirst mode of operation, data need not pass through the column repaircircuit. Thus, an operation of the column repair circuit is notperformed. This means that a high-speed data transfer is achieved whenECC processing is executed. The second data bus may have a bus widthcorresponding to conventional repair efficiency. By this, a circuit sizeof the column repair circuit does not increase, so that an increase in achip size is suppressed.

FIG. 12 is a block diagram schematically illustrating a NAND flashmemory according to an embodiment of the inventive concepts. Referringto FIG. 12, a NAND flash memory 10 comprises a memory array 101, a pagebuffer 102, a column coding circuit 103, a main column repairmultiplexer (a column repair circuit) 104, a parity column repaircircuit (Parity CRMUX) 105, an ECC column coding circuit 108, an I/O pad106, and an ECC engine (or, an ECC circuit) 107. In FIG. 12, constituentelements that have the same function as those in FIG. 21 are marked bythe same reference numerals, and a description thereof is thus omitted.In FIG. 12, DataBus_(—)1, DataBus_(—)2, and DataBus_(—)3 (a second databus) are lines through which data is exchanged between a page buffer 82and the I/O pad 106. Below, such lines are referred to as a data bus.Also, ECCBus_(—)1, ECCBus_(—)2, ECCBus_(—)3 (a first data bus) are linesthrough which data is exchanged between the page buffer 82 and the ECCcircuit 107. Below, such lines are referred to as ECC_Bus.

The NAND flash memory 10 is different from a NAND flash memory shown inFIG. 21 in that it includes a column coding circuit 103 and an ECCcoding circuit 108 instead of a column coding circuit 83. A columnaddress is provided to the column coding circuit 103 and the ECC columncoding circuit 108. The column coding circuit 103 and the ECC columncoding circuit 108 output a selection signal Sel_A or a selection signalSel_B to a PB control circuit 60 of the page buffer 102 to connect anoutput of a page buffer to either ECCBus_(—)1 or DataBus_(—)1 from aportion (e.g., a portion formed of a multiplexer 52 _(—) b and a PBcontrol circuit 83_1 shown in FIG. 22) directly connected to the pagebuffer 102.

In particular, the ECC column coding circuit 108 receives a columnaddress (hereinafter, marked by Address B) from an ECC circuit 107 andoutputs the selection signal Sel_B on a PB control circuit 60independently from a column address provided to the column codingcircuit 103 from an address control circuit (not shown). In this case,an output of the page buffer 102 is connected to ECCBus_(—)1. By this,address control is separately executed when an output of the page buffer102 is connected to ECCBus_(—)1 or DataBus_(—)1.

In a conventional NAND flash memory, an output (a data bus)(hereinafter, referred to as an IO bus for distinction) of a page bufferis shared at a first mode of operation and a second mode of operation.In the NAND flash memory 10, the IO bus being an output of the pagebuffer is independently prepared without sharing at the first mode ofoperation and the second mode of operation.

By this, a path between an output of the page buffer and an input of theECC circuit 107 does not include a circuit influencing a high-speed datatransfer of a column repair circuit 104. That is, a data transfer isexecuted in high speed. Also, a second data bus is set to a bus widthcorresponding to conventional repair efficiency. By this, a circuit sizeof the column repair circuit 104 does not increase, so that an increasein a chip size is suppressed. In the event that a design of the NANDflash memory 10 is changed to that of a NAND flash memory not includingan ECC circuit, it is possible to eliminate the ECC column codingcircuit 108, the parity column repair circuit 104, ECCBus_(—)1 toECCBus_(—)3, and the ECC circuit 107. This means that it is easy todesign.

The page buffer 102, as shown in FIG. 12, comprises PB (Page Buffer)(hereinafter, referred to as a page buffer 102 a), PB_CR (hereinafter,referred to as a page buffer 102 b), PB_Parity (hereinafter, referred toas a page buffer 102 c), and PB_PCR (hereinafter, referred to as a pagebuffer 102 d). The page buffer 102 a is a page buffer (e.g., a firstpage buffer) that amplifies a voltage of a bit line connected to anormal memory cell and latches the amplified result. When the selectionsignal Sel_A is received from the column coding circuit 103 at a dataread operation of a normal mode (e.g., a second mode of operation), thepage buffer 102 a outputs the amplified result to the I/O pad 106through DataBus_(—)1, DataBus_(—)2, and DataBus_(—)3 (e.g., a seconddata bus) as read data Data_Out_A. Meanwhile, when the selection signalSel_A is received from the ECC column coding circuit 108 at a data readoperation of an ECC mode (e.g., a first mode of operation), the pagebuffer 102 a outputs the amplified result to the ECC circuit 107 throughECCBus_(—)1, ECCBus_(—)2, and ECCBus_(—)3 (e.g., a first data bus) asread data Data_Out_B.

If the selection signal Sel_A is received from the column coding circuit103 at a data write operation of the normal mode, the page buffer 102 areceives, as write data Data_In_A, write data through DataBus_(—)3,DataBus_(—)2, and DataBus_(—)1. If the selection signal Sel_B isreceived from the ECC column coding circuit 108 at a data writeoperation of the ECC mode, the page buffer 102 a receives, as write dataData_In_B, a result of ECC processing through ECCBus_(—)3, ECCBus_(—)2,and ECCBus_(—)1.

The page buffer 102 b is a page buffer (e.g., a second page buffer) thatis replaced together with a normal memory cell and a bit line. That is,in the event that one of page buffer units constituting the page buffer102 a is abnormal, the abnormal page buffer unit is repaired with one ofpage buffer units in the page buffer 102 b. The page buffer 102 boperates substantially the same as that of the page buffer 102 a, and adescription thereof is thus omitted. The column repair circuit 104 is acircuit for replacing a page buffer unit of the page buffer 102 a with apage buffer unit of the page buffer 102 b. If a column address (e.g., aselection signal Sel_A) for selecting an abnormal page buffer unit ofthe page buffer 102 a is provided to the column coding circuit 103, thecolumn coding circuit 103 controls to select a page buffer unit of thepage buffer 102 b.

The page buffer 102 c is a page buffer (e.g., a third page buffer) thatamplifies a voltage of a bit line connected to a parity memory cell(formed of a memory cell transistor for ECC processing configured thesame as a normal memory cell) and latches the amplified result. Inaddition, parity data a parity memory cell stores is not output to theexterior through the I/O pad 106 at a normal mode. Meanwhile, if aselection signal Sel_B is received from the ECC column coding circuit108 at a data read operation of the ECC mode, the page buffer 102 coutputs the amplified result to the ECC circuit 107 through ECCBus_(—)1,ECCBus_(—)2, and ECCBus_(—)3 as read data Data_Out_B.

Also, parity data a parity memory cell stores is not received from theexterior through the I/O pad 106 at the normal mode. Meanwhile, if theselection signal Sel_B is received from the ECC column coding circuit108 at a data write operation of the ECC mode, the page buffer 102 creceives parity data being a result of ECC processing of the ECC circuit107 through ECCBus_(—)3, ECCBus_(—)2, and ECCBus_(—)1 as write dataData_Out_B.

The page buffer 102 d is a page buffer (e.g., a fourth page buffer) thatis replaced together with a parity memory cell and a bit line when theparity memory cell or the bit line connected to the page buffer 102 c isabnormal. That is, in the event that one of page buffer unitsconstituting the page buffer 102 c is abnormal, the abnormal page bufferunit is repaired with one of page buffer units in the page buffer 102 d.The page buffer 102 d operates substantially the same as that of thepage buffer 102 c, and a description thereof is thus omitted.

The parity column repair circuit 105 is a circuit for replacing a pagebuffer unit of the page buffer 102 c with a page buffer unit of the pagebuffer 102 d. If a column address (e.g., a selection signal Sel_B) forselecting an abnormal page buffer unit of the page buffer 102 c isprovided to the ECC column coding circuit 108, the ECC column codingcircuit 108 controls to select a page buffer unit of the page buffer 102d.

The page buffers 102 a to 102 d of the page buffer 102 are configured bythe same circuit. Below, the circuit structure will be more fullydescribed with reference to FIGS. 2 to 17. FIG. 13 is a diagramschematically illustrating a portion corresponding to a page buffer 102,a column coding circuit 103, and an ECC column coding circuit 108 shownin FIG. 12. FIGS. 14A and 14B are diagrams schematically illustrating aPB 410 unit and a PB unit shown in FIG. 13. FIG. 15 is a circuit diagramschematically illustrating a PB unit. FIG. 16 is a circuit diagramschematically illustrating a PB unit according to another embodiment.FIG. 17 is a circuit diagram schematically illustrating a bit internalcircuit 50 _(—) i (i being an integer of 0 to 7) shown in FIGS. 15 and16.

Referring to FIG. 12, a portion corresponding to a page buffer 102, acolumn coding circuit 103, and an ECC column coding circuit 108 shown inFIG. 12 has a PB4IO unit that latches four data from four IO lines andwrites data with respect to four IO lines.

In FIG. 13, there are shown ten PB4 IOs, that is, PB0 IO 0123 (PB 4IOunit) 30_0, PB0 IO 4567 (PB 4IO unit) 30_1, PB1 IO 0123 (PB 4IO unit)30_2, PB1 IO 4567 (PB 4IO unit) 30_3, PB2 IO 0123 (PB 4IO unit) 30_4,PB2 IO 4567 (PB 4IO unit) 30_5, PB3 IO 0123 (PB 4IO unit) 30_6, PB3 IO4567 (PB 4IO unit) 30_7, PB4 IO 0123 (PB 4IO unit) 30_8, and PB4 IO 4567(PB 4IO unit) 30_9.

Here, an IO line is an input/output line installed between a multiplexer52 _(—) b and a PB control circuit 60 of a PB unit as will be more fullydescribed below. In exemplary embodiments, the IO line is electricallyconnected to any one of eight bit lines through a multiplexer 52 _(—) band eight bit circuits 51_0 a to 51_7 a. That is, the IO line is asignal line through which memory cell transistor data or data read froma memory cell transistor is transferred.

Since PB 4IO units shown in FIG. 13 have the same structure, a PB 4IOunit 30_0 shown in FIG. 13 is illustrated in FIG. 14A. The PB 4IO unit30_0 is formed of four PB units 30_00 to 30_03.

When an active level (e.g., a high level) of selection signal Sel_A<0>is provided from a column coding circuit 103, each of the PB units 30_00to 30_03 connects an IO line and a data bus (e.g., a second bus) (aswill be described below, a data bus Data_A<7:0>). In this case, asillustrated in FIG. 14A, four read data bits Data_Out_A<0> toData_Out_A<3> are read from four IO lines onto a data bus Data_A<3:0>.

Also, when an active level (e.g., a high level) of selection signalSel_B<0> is provided from an ECC column coding circuit 108, each of thePB units 30_00 to 30_03 connects an IO line and an ECC bus (e.g., afirst bus) (as will be described below, a data bus Data_B<19:0>). Inthis case, as illustrated in FIG. 14A, four read data bits Data_Out_A<0>to Data_Out_A<3> are read from four IO lines onto a data busData_B<3:0>.

Referring to FIG. 14B, each of PB units shown in FIG. 14A compriseseight bit circuits 51_1 a to 51_7 a (configured the same as those inFIG. 22), a multiplexer 52 _(—) b (shown in FIG. 22), and a page buffer(PB) control circuit 60. First, a detailed circuit of a PB unit will bemore fully described with reference to FIGS. 15 and 17. FIG. 17 shows acircuit of each of bit internal circuits 50_0 to 50_7 shown in FIG. 15.FIG. 17 shows a data sensing unit and a latch unit at a write operationand a driver unit for driving a signal line at a read operation. Inparticular, each of the bit internal circuits 50_0 to 50_7 isimplemented using transistors and inverter circuits. In addition, acombination of bit circuits 51_0 a to 51_7 a and a multiplexer 52 _(—) bshown in FIG. 14B corresponds to the bit internal circuits 50_0 to 50_7.That is, since a bit internal circuit is selected by a selection signalDIO, it partially has a function of a bit circuit and a multiplexer 52_(—) b. Also, a bit internal circuit shown in FIG. 17 is the same as abit internal circuit of a conventional PB unit shown in FIG. 22.

As illustrated in FIG. 17, a bit internal circuit 50 _(—) i (i being aninteger of 0 to 7) is formed of an inverter circuit 511, an invertercircuit 512, a transistor 513, a transistor 514, a transistor 515, atransistor 521, and a transistor 522. Here, the transistors 513, 514,515, 521, and 522 may be an N-channel MOS transistor.

A latch unit of the bit internal circuit 50 _(—) i is formed of theinverter circuits 511 and 512. Here, an input terminal of the inverter511 and an output terminal of the inverter 512 are connected to aconnection node N1, and an output terminal of the inverter 511 and aninput terminal of the inverter 512 are connected to a connection nodeN2. The connection node N1 is connected to a memory cell transistor (notshown) through a bit line. Data that a memory cell transistor storesappears on the connection node N1 as Data_i at a read operation. Datathat is to be stored in a memory cell transistor appears on theconnection node N1 as Data_i at a write operation. For example, when amemory cell transistor stores a low level (data 0), a voltage of Data_ihas a low level. When a memory cell transistor stores a high level (data1), a voltage of Data_i has a high level.

In the bit internal circuit 50 _(—) i, a driver unit is formed of thetransistors 515 and 522. The transistor 522 has a drain connected to aline of a read signal RD, a gate connected to a line of a selectionsignal DIO<i>, and a source connected to a drain of the transistor 515.The transistor 515 has a gate connected to the source of the transistor522, a gate connected to the connection node N2, and a source grounded.Here, the selection signal DIO<i> (i being 0˜7) is Sub BL Coding shownin FIG. 14A. For example, a column coding circuit 103 makes one ofselection signals DIO<7:0> become high based on a 3-bit address signalprovided from an address control circuit (not shown), or an ECC columndecoding circuit 108 makes one of the selection signals DIO<i> becomehigh based on a 3-bit address signal provided from an ECC circuit 107.By this, one of bit internal circuits 50_0 to 50_7 shown in FIG. 15 isselected.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data read operation on a memory cell transistor, alogical level of the read signal RD is equal to that of Data_i. That is,for example, when Data_i is at a high level with the read signal RDbeing pre-charged to a high level, the transistor 515 is turned off, thetransistor 522 is turned on, and the read signal RD retains a highlevel. When Data_i is at a low level, the transistor 515 is turned on,the transistor 522 is turned on, and the bit internal circuit 50 _(—) ichanges the read signal RD from a high level to a low level. A line ofthe read signal RD is connected to a PB control circuit 60 as shown inFIG. 15. At a first mode of operation (e.g., an ECC mode), a line of theread signal RD is connected to ECCBus in response to a selection signalSel_B (a column address signal the ECC column coding circuit 108outputs). By this, Data_i of the bit internal circuit 50 _(—) i isoutput on ECCBus as a data read signal Data_Out_B.

Meanwhile, at a second mode of operation (e.g., a normal mode), a lineof the read signal RD is connected to DataBus in response to a selectionsignal Sel_A (a column address signal a column coding circuit 103outputs). By this, Data_i of the bit internal circuit 50 _(—) i isoutput on DataBus as a data read signal Data_Out_A.

Returning to FIG. 17, the transistors 513, 514, and 521 constitute asensing unit of the bit internal circuit 50 _(—) i. The transistor 513has a drain connected to the connection node N1, a gate connected to aline of a write signal DI, and a source connected to a drain of thetransistor 521. The transistor 514 has a drain connected to theconnection node N2, a gate connected to a line of a write signal nDI,and a source connected to the drain of the transistor 521. Thetransistor 521 has a drain connected to the source of the transistor 513and the source of the transistor 513, a gate connected to a line of aselection signal DIO<i>, and a source grounded.

The lines of the write signals DI and nDI are connected to the PBcontrol circuit 60 as shown in FIG. 15. As will be described below, as adata bus and ECCBus are connected by the selection signal Sel_B at thefirst mode of operation, a data write signal Data_In_B is received fromECCBus. By this, the PB control circuit 60 varies one of the writesignals DI and nDI from a low level to a high level in response to alevel of the data write signal Data_In_B. At this time, the other of thewrite signals DI and nDI retains a low level. Meanwhile, at the secondmode of operation, connection to DataBus is performed by the selectionsignal Sel_A, and a data write signal Data_In_A is received fromDataBus. By this, the PB control circuit 60 varies one of the writesignals DI and nDI from a low level to a high level in response to alevel of the data write signal Data_In_A. At this time, the other of thewrite signals DI and nDI retains a low level.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data write operation on a memory cell transistor, aData_i level of the bit internal circuit 50 _(—) i is decided accordingto levels of the write signals DI and nDI. More particular, when one ofa data write signal Data_In_A and a data write signal Data_In_B is at alow level (data 0), the PB control circuit 60 outputs a high level ofwrite signal DI and a low level of write signal nDI. By this, thetransistor 513 is turned on and the transistor 514 is turned off. Atthis time, the connection node N1 is set to a low level and theconnection node N2 is set to a high level, so that Data_i has the samelogical low level (data 0) as that of a data bus.

When the data write signal Data_In_A or the data write signal Data_In_Bis at a high level (data 1), the PB control circuit 60 outputs a lowlevel of write signal DI and a high level of write signal nDI. By this,in the bit internal circuit 50 _(—) i, the transistor 513 is turned offand the transistor 514 is turned on. At this time, the connection nodeN1 is set to a high level and the connection node N2 is set to a lowlevel, so that Data_i has the same logical high level (data 1) as thatof a data bus.

Returning to FIG. 17, the PB control circuit 60 comprises a write unitperforming a data transfer from a data bus to a page buffer and a readunit performing a data transfer from a page buffer to a data bus. Theread unit of the PB control circuit 60 is formed of transistors 61 a and61 b. The transistors 61 a and 61 b may be an NMOS transistor. Thetransistor 61 a has a drain connected to a line of the read signal RD, agate connected to a line of the selection signal Sel_A, and a sourceconnected to DataBus (e.g., a second data bus). The transistor 61 b hasa drain connected to a line of the read signal RD, a gate connected to aline of the selection signal Sel_B, and a source connected to ECCBus(e.g., a first data bus).

Here, the selection signal Sel_A may be a column address signal that acolumn coding circuit 103 generates in response to address bits, forexample, an address Address A received from an address control circuit(not shown). The selection signal Sel_B may be a column address signalthat an ECC column coding circuit 108 generates in response to a part ofaddress bits, for example, an address Address B received from an ECCcircuit 107 shown in FIG. 12.

If a high level of selection signal Sel_B is received from the columnECC coding circuit 108 at a data read operation of an ECC mode (e.g., afirst mode of operation), the read unit of the PB control circuit 60turns on the transistor 61 b such that a line of the read signal RD isconnected to ECCBus. By this, data of memory cell transistors (Data_i ofa bit internal circuit) stored in the bit internal circuits 50_0 to 50_7are output to ECCBus as a data read signal Data_Out_B. If a high levelof selection signal Sel_A is received from the column coding circuit 103at a data read operation of a normal mode (e.g., a second mode ofoperation), the read unit of the PB control circuit 60 turns on thetransistor 61 a such that a line of the read signal RD is connected toDataBus. By this, data of memory cell transistors stored in the bitinternal circuits 50_0 to 50_7 are output to DataBus as a data readsignal Data_Out_A.

The read unit of the PB control circuit 60 has the following structuresuch that when a memory cell transistor or a bit line connected to amemory cell transistor is abnormal in the page buffers 102 a and 102 c,data provided to the ECC circuit 107 has fixed data (e.g., fixed to data0) at a data read operation of an ECC mode. That is, the read unit ofthe PB control circuit 60 comprises a defect information storing unit 90a and a data fixing unit 90 b as illustrated in FIG. 15.

The defect information storing unit 90 a comprises inverter circuits 92and 93 and transistors 94, 95, and 96. Here, the transistors 94, 95, and96 may be an N-channel MOS transistor. A latch unit of the defectinformation storing unit 90 a is formed of the inverter circuits 92 and93. The inverter circuit 92 has an output terminal connected to aconnection node N4 and an input terminal of the inverter 93 and an inputterminal connected to a connection node N3 and an output terminal of theinverter circuit 94. The connection node N3 is connected to a firstinput terminal of the AND circuit 91. The connection node N3 provides adefect signal PB_Defect indicating that data stored in the latch unit isdefective. The connection node N4 provides a defect signal nPB_Defectindicating that data stored in the latch unit is defective.

A sensing unit of the defect information storing unit 90 a comprisestransistors 94, 95, and 96. The transistor 94 has a drain connected tothe connection node N3, a gate connected to a line of a defectinformation signal SDI, and a source connected to a drain of thetransistor 96. The transistor 95 has a drain connected to the connectionnode N4, a gate connected to a line of a defect information signal nSDI,and a source connected to the drain of the transistor 96. The transistor96 has a drain connected to the source of the transistor 94 and thesource of the transistor 95, a gate connected to a line of a power-onreset signal POR_Mode, and a source grounded.

Here, the defect information signal SDI and the defect informationsignal nSDI are signals indicating whether a bit line connected to thePB control circuit 60 or a memory cell transistor connected to acorresponding bit line is defective. In the event that a test resultexecuted after fabrication indicates that a bit line connected to the PBcontrol circuit 60 is defective, the defect information signal SDI isset to data 0 (e.g., a low level) and the defect information signal nSDIis set to data 1 (e.g., a high level). Or, in the event that a testresult executed after fabrication indicates that a bit line connected tothe PB control circuit 60 is defective, the defect information signalSDI is set to a high level and the defect information signal nSDI is setto a low level. Before shipment, such defect information signals arestored at a storage area for system, for example, of the NAND flashmemory 10 in connection with the selection signal Sel_B indicating alocation of the PB control circuit 60. Also, the power-on reset signalPOR_Mode is a signal maintaining a high level during a predeterminedtime period (e.g., a time period where the defect information signalsare transferred to the PB control circuit 60 from the storage area forsystem) after the NAND flash memory 10 is powered up.

When the NAND flash memory 10 is powered up, the power-on reset signalPOR_Mode goes to a high level. If a bit line connected to the PB controlcircuit 60 is defective, the defect information storing unit 90 a turnsoff the transistor 94 and turns on the transistor 95. By this, the nodeN3 is set to a high level and the node N4 is set to a low level. In thiscase, the defect signal PB_Defect has a high level. Since the power-onreset signal POR_Mode goes to a low level after a transfer period, thedefect information storing unit 90 a maintains the defect signalPB_Defect at a high level during a period where a power is supplied tothe NAND flash memory 10.

When the NAND flash memory 10 is powered up, the power-on reset signalPOR_Mode goes to a high level. If a bit line connected to the PB controlcircuit 60 is not defective, the defect information storing unit 90 aturns on the transistor 94 and turns off the transistor 95. By this, thenode N3 is set to a low level and the node N4 is set to a high level. Inthis case, the defect signal PB_Defect has a low level. Since thepower-on reset signal POR_Mode goes to a low level after a transferperiod, the defect information storing unit 90 a maintains the defectsignal PB_Defect at a low level during a period where a power issupplied to the NAND flash memory 10.

The data fixing unit 90 b is formed of the AND circuit 91 and atransistor 61 c. Here, the transistor 61 c is an NMOS transistor. TheAND circuit 91 is a 2-input 1-output logic circuit. The AND circuit 91has a first input terminal connected to the connection node N3 and asecond input terminal connected to a line of the selection signal Sel_A,and an output terminal connected to a gate of the transistor 61 c. Thetransistor 61 c has a drain connected to a line of a read signal RD, agate connected to the output terminal of the AND circuit 91, and asource grounded.

In the event that a bit line connected to the PB control circuit 60 isnot defective, the defect signal PB_Defect has a low level. In thiscase, since the AND gate 91 outputs a low level of output signal, thetransistor 61 c of the data fixing unit 90 b is turned off. That is, thedata fixing unit 90 b does not operate. Meanwhile, in the event that abit line connected to the PB control circuit 60 is defective, the defectsignal PB_Defect has a high level. When ECC is used, that is, at an ECCmode, if a high level of selection signal Sel_B is provided to the ANDcircuit 91, the AND circuit 91 outputs a high level of output signal, sothat the transistor 61 c is turned on. In this case, ECCBus_(—)1 isgrounded such that Data_Out_B is fixed to a low level (e.g., a GNDlevel). That is, in the event that a bit line connected to the PBcontrol circuit 60 is defective, at the ECC mode, the PB control circuit60 acts as a data fixing circuit that outputs read data Data_Out_Bhaving a fixed level (e.g., a low level) to ECCBus_(—)1.

In addition, at a data read operation of a normal mode, since the PBcontrol circuit 60 is selected by the selection signal Sel_A, the ANDcircuit 91 outputs a low-level signal. In this case, the data fixingunit 90 b being an additional circuit does not operate. If the defectsignal PB_Defect is directly provided to a gate of the transistor 91 cwithout using the AND circuit 91, the read signal RD is fixed to a lowlevel when a bit line connected to the PB control circuit 60 isdefective. That is, the PB control circuit 60 acts as a data fixingcircuit that outputs a fixed level (e.g., a low level) of read dataData_Out_A on DataBus_(—)1 when the selection signal Sel_A is receivedat a normal mode and outputs a low level of read data Data_Out_B whenthe selection signal Sel_B is received at an ECC mode.

The defect information storing unit 90 a and the data fixing unit 90 bshown in FIG. 15 may be configured as illustrated in FIG. 16. FIG. 16shows another circuit structure of a PB unit. In FIG. 16, constituentelements that are the same as those in FIG. 15 are marked by the samereference numerals, and a description thereof is thus omitted. Thedefect information storing unit 90 a shown in FIG. 16 is configured thesame as that shown in FIG. 15. But, the data fixing unit 90 b shown inFIG. 15 is replaced with a data fixing unit 90 b′. A signal on aconnection node N4 of the defect information storing unit 90 a is usedas a defect signal nPB_Defect. The data fixing unit 90 b′ is formed of atransistor 61 c. The transistor 61 c has a source connected to ECCBus(e.g., a first data bus). The transistor 61 b has a drain connected to aline of the read signal RD, a gate connected to a line of the selectionsignal Sel_B, and a source connected to a drain of the transistor 61 c.

In the event that a bit line connected to the PB control circuit 60 isdefective, the defect signal nPB_Defect has a low level. In this case,since the transistor 61 c is turned off, a transfer path between theread signal RD and ECCBus_(—)1 is blocked. For this reason, read dataData_Out_B is fixed to a high level through a pull-up circuit.Meanwhile, in the event that a bit line connected to the PB controlcircuit 60 is not defective, the defect signal nPB_Defect has a lowlevel. In this case, since the transistor 61 c is turned on. By this,the read signal RD, that is, data of a memory cell transistor is outputonto ECCBus_(—)1 such that it is read as read data Data_Out_B. Ascompared with a data fixing unit 90 b, the data fixing unit 90 b′ hassuch a merit that an AND circuit is not required since the transistors61 b and 61 c are connected in series between a line of the read signalRD and ECCBus_(—)1.

In the data fixing unit 90 b′ shown in FIG. 16, if the transistor 61 cis inserted between a line of the read signal RD and the transistor 61 aand a drain of the transistor 61 b, that is, between a line of the readsignal RD and the PB control circuit 60, the PB control circuit 60 actsas a data fixing circuit that outputs a fixed level (e.g., a high level)of read data Data_Out_A to DataBus_(—)1 in response to the selectionsignal Sel_A provided at the normal mode and a high level of read dataData_Out_B in response to the selection signal Sel_B provided at the ECCmode. As described above, in the event that a bit line connected to thePB control circuit 60 is defective, data Data_Out_A or Data_Out_B mayhave a low level or a high level of fixed value.

Returning to FIG. 15, the write unit of the PB control circuit 60comprises inverter circuits 62, 63, 67, NAND circuits 64 and 65, an ORcircuit 66, and switches 68 and 69. The inverter circuit 62 is a logicalinversion circuit, and has an output terminal connected to a line of thewrite signal DI and an input terminal connected to an output terminal ofthe NAND circuit 64. The inverter circuit 63 is a logical inversioncircuit, and has an output terminal connected to a line of the writesignal nDI and an input terminal connected to an output terminal of theNAND circuit 65.

The NAND circuit 64 is a 3-input 1-output NAND circuit, and has a firstinput terminal connected to a line of a write enable signal fDinEnable,a second input terminal connected to an output terminal of the ORcircuit 66, and a third input terminal connected to an output terminalof the inverter circuit 67. An output terminal of the NAND circuit 64 isconnected to an input terminal of the inverter circuit 62. The NANDcircuit 65 is a 3-input 1-output NAND circuit, and has a first inputterminal connected to a line of the write enable signal fDinEnable, asecond input terminal connected to the output terminal of the OR circuit66, and a third input terminal connected to a first input/outputterminal of the switch 68 and a first input/output terminal of theswitch 69. An output terminal of the NAND circuit 65 is connected to aninput terminal of the inverter circuit 63.

The OR circuit 66 is a 2-input 1-output logic circuit, and has a firstinput terminal connected to an output of an AND circuit 71 and a secondinput terminal connected to a line of the selection signal Sel_A. Anoutput terminal of the OR circuit 66 is connected to the second inputterminal of the NAND circuit 64 and the second input terminal of theNAND circuit 65. The AND circuit 71 logically combines the selectionsignal Sel_B and the defect signal nPB_Defect. By this, in a case wherethe defect signal nPB_Defect has a high level (not defective), theselection signal Sel_B has a high level. At this time, the second inputterminal of the NAND circuit 65 has a high level, so that a writecondition is satisfied. Meanwhile, in a case where the defect signalnPB_Defect has a low level (e.g., a defective page buffer), at a mode ofoperation of the selection signal Sel_B, the second input terminal ofthe NAND circuit 65 does not have a high level. Thus, a write conditionis not satisfied. The inverter circuit 67 is a logical inversioncircuit, and has an input terminal connected to the first input/outputterminal of the switch 68 and the first input/output terminal of theswitch 69 and an output terminal connected to the third input terminalof the NAND gate 64.

The switch 68 is a bidirectional switch, and has the first input/outputterminal connected to the input terminal of the inverter circuit 67 andthe third input terminal of the NAND circuit 65 and a secondinput/output terminal connected to DataBus. The switch 69 is abidirectional switch, and has the first input/output terminal connectedto the input terminal of the inverter circuit 67 and the third inputterminal of the NAND circuit 65 and a second input/output terminalconnected to ECCBus. In addition, an input of the inverter circuit 67 ispulled up by a PMOS transistor such that an input of the invertercircuit 67 is not set to a “don't care” state when any one of thebidirectional switches is unselected.

With the above-described structure, when at a data write operation ofthe ECC mode (e.g., a first mode of operation), the write enable signalfDinEnable is at a high level and the selection signal Sel_B is at ahigh level, the write unit of the PB control circuit 60 turns on theswitch 69 such that one of the write signals DI and nDI transitions froma low level to a high level in response to a level of the data writesignal Data_In_B received from ECCBus. More particular, when the datawrite signal Data_In_B is at a low level (data 0), the write signal DItransitions to a high level. By this, Data_i of one of the bit internalcircuits 50_0 to 50_7 goes to a low level. Afterwards, data 0 is writtenat a memory cell transistor through a program operation.

Meanwhile, when the data write signal Data_In_B is at a high level (data1), the write signal nDI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a high level.Afterwards, data 1 is written at a memory cell transistor through aprogram operation.

If the write enable signal fDinEnable and the selection signal Sel_A goto a high level at a data write operation of a normal mode (e.g., asecond mode of operation), the write unit of the PB control circuit 60turns on the switch 68 such that one of the write signals DI and nDItransitions from a low level to a high level in response to a level ofthe data write signal Data_In_A received from DataBus. More particular,when the data write signal Data_In_A is at a low level (data 0), thewrite signal DI transitions to a high level. By this, Data_i of one ofthe bit internal circuits 50_0 to 50_7 goes to a low level. Afterwards,data 0 is written at a memory cell transistor through a programoperation.

Meanwhile, when the data write signal Data_In_A is at a high level (data1), the write signal nDI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a high level.Afterwards, data 1 is written at a memory cell transistor through aprogram operation.

As described above, the PB control circuit 60 is a circuit that controlsa data transfer between a data bus (a first data bus and a second databus) and a memory cell transistor connected through a bit line to one,selected by the selection signal DIO<i>, from among the bit internalcircuits 50_0 to 50_7 constituting a PB unit of a page buffer 102.

The line of the read signal RD, the line of the write signal DI, and theline (IO line) of the write signal nDI are lines connecting the PBcontrol circuit 60 and the bit internal circuits 50_0 to 50_7constituting the PB unit, and are input/output lines for a data transferof the PB unit. Thus, the PB control circuit 60 transfers write data andread data between an input/output unit of the page buffer 102 and thefirst and second data buses ECCBus and DataBus.

Returning to FIG. 14A, by the above-described PB control circuit 60, aPB 4IO unit 30_0 operates as follows. When a high level of selectionsignal Sel_A<0> is received from the column coding circuit 103, the PB4IO unit 30_0 connects input/output lines IO_0 to IO_3 (in FIG. 15,marked by RD) of four page buffers to a 4-bit data bus Data_A<3:0>. Bythis, the PB 4IO unit 30_0 outputs the data read signals Data_Out_A<3>to Data_Out_A<0> (hereinafter, referred to as data read signalsData_Out_A<3:0>) on the data bus Data_A<3:0>.

When a high level of selection signal Sel_B<0> is received from the ECCcolumn coding circuit 108, the PB 4IO unit 30_0 connects input/outputlines IO_0 to IO_3 of four page buffers to a 4-bit ECC bus Data_B<3:0>(here, referred to as data bus Data_B<3:0>). By this, the PB 4IO unit30_0 outputs the data read signals Data_Out_B<3> to Data_Out_B<0>(hereinafter, referred to as data read signals Data_Out_B<3:0>) on thedata bus Data_B<3:0>.

Returning to FIG. 13, by the above-described PB 4IO unit 30_0, a pagebuffer 102, a column coding circuit 103 and an ECC column coding circuit108 (here, referred to as a data read model) operate as follows at adata read operation. Also, input/output lines (e.g., data read lines RDshown in FIG. 4) of page buffers connected to PB 4IO units 30_1 to 30_9shown in FIG. 13 are referred to as IO lines IO_4 to IO_7, IO lines IO_8to IO_11, IO lines IO_12 to IO_15, IO lines IO_16 to IO_19, IO linesIO_20 to IO_23, IO lines IO_24 to IO_27, IO lines IO_28 to IO_31, IOlines IO_32 to IO_35, and IO lines IO_36 to IO_39. Also, DataBus has an8-bit bus width, and is referred to as a data bus Data_A<7:0>. ECCBushas a 20-bit bus width, and is referred to as a data bus Data_B<19:0>.

At the normal mode (e.g., the second mode of operation), the columncoding circuit 103 sets one of column addresses of selection signalsSel_A<0> to Sel_A<4> to a high level and the remaining thereof to a lowlevel and then the selection signals Sel_A<0> to Sel_A<4> to the dataread model. For example, at the normal mode, 40-bit data of the IO linesIO_0 to IO_39 is sequentially output onto the data bus Data_A<7:0> bysequentially providing the selection signals Sel_A<0> to Sel_A<4> to thedata read model.

When the selection Sel_A<0> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0 and the PB 4IO unit 30_1 connect the IO lines IO_0 to IO_7 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_0 and the PB 4IO unit30_1 output read data Data_Out_A<7:0> (data on the IO lines IO_0 toIO_7) on the data bus Data_A<7:0>.

When the selection Sel_A<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_2 and the PB 4IO unit 30_3 connect the IO lines IO_8 to IO_15 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_2 and the PB 4IO unit30_3 output read data Data_Out_A<7:0> (data on the IO lines IO_8 toIO_15) on the data bus Data_A<7:0>.

When the selection Sel_A<2> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_4 and the PB 4IO unit 30_5 connect the IO lines IO_16 to IO_23 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_4 and the PB 4IO unit30_5 output read data Data_Out_A<7:0> (data on the IO lines IO_16 toIO_23) on the data bus Data_A<7:0>.

When the selection Sel_A<3> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_6 and the PB 4IO unit 30_7 connect the IO lines IO_24 to IO_31 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_6 and the PB 4IO unit30_7 output read data Data_Out_A<7:0> (data on the IO lines IO_24 toIO_31) on the data bus Data_A<7:0>.

Finally, when the selection Sel_A<4> goes to a high level, thetransistor 61 a of the PB control circuit 60 is turned on. At this time,the PB 4IO unit 30_8 and the PB 4IO unit 30_9 connect the IO lines IO_32to IO_39 to the data bus Data_A<7:0>. By this, the PB 4IO unit 30_8 andthe PB 4IO unit 30_9 output read data Data_Out_A<7:0> (data on the IOlines IO_32 to IO_39) on the data bus Data_A<7:0>.

As described above, if the selection signal Sel_A is provided to thedata read model five times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_A<7:0> by the 8-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on DataBusthrough bit lines and IO lines IO_0 to IO_39.

At the ECC mode (e.g., the first mode of operation), the ECC circuit 107sets one of column addresses of the selection signals Sel_B<0> andSel_B<1> to a high level and the other to a low level and outputs themto the data read model. 40-bit data of the IO lines IO_0 to IO_39 issequentially read on a data bus Data_B<19:0> by sequentially providingthe selection signals Sel_B<0> and Sel_B<1> to the data read mode.

When the selection Sel_B<0> goes to a high level, the transistor 61 b ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0, 30_2, 30_4, 30_6, and 30_8 connect the data bus Data_B<19:0> to IOlines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, andIO_32 to IO_35. By this, the PB 4IO unit 30_0, 30_2, 30_4, 30_6, and30_8 output read data Data_Out_B<19:0> (data on the IO lines IO_0 toIO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32 to IO_35)on the data bus Data_B<19:0>.

When the selection Sel_B<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_1, 30_3, 30_5, 30_7, and 30_9 connect the data bus Data_B<19:0> to IOlines IO_4 to IO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, andIO_36 to IO_39. By this, the PB 4IO unit 30_1, 30_3, 30_5, 30_7, and30_9 output read data Data_Out_B<19:0> (data on the IO lines IO_4 toIO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, and IO_36 toIO_39) on the data bus Data_B<19:0>.

As described above, if the selection signal Sel_B is provided to thedata read model two times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_B<19:0> by the 20-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on ECCBusthrough bit lines and IO lines IO_0 to IO_39. For example, when aselection signal is not provided five times at the normal mode, data onIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not read on DataBus. If a selection signal (e.g.,Sel_B<0>) is provided once at the ECC mode, data of the IO lines IO_0 toIO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32 to IO_35may be read out on ECCBus.

FIG. 18 is a diagram for describing a data write operation of a portioncorresponding to a page buffer 102, a column coding circuit 103 and anECC column coding circuit 108 shown in FIG. 12. A data write operationof a page buffer 102, a column coding circuit 103 and an ECC columncoding circuit 108 (here, referred to as a data write model) isperformed by an operation of a PB 4IO unit 30_0. A data transfer of thedata write model is performed in a direction opposite to a directionshown in FIG. 12, and a description thereof is thus omitted.

In the data write model, for example, at a normal mode, data provided toIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not written from DataBus when a selection signalis not provided five times. In this behalf, if a selection signal (e.g.,Sel_B<0>) is provided once at the ECC mode, the remaining data iswritten on the IO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19,IO_24 to IO_27, and IO_32 to IO_35 from ECCBus.

A semiconductor memory device (or, a semiconductor memory device) 10 ofthe inventive concepts comprises a first data bus Data_B<19:0>, a seconddata bus Data_A<7:0> being different in number from the first data busand independent from the first data bus Data_B<19:0>, and a datatransfer unit (e.g., a PB control circuit 60 of each of PB 4IO units30_0 to 30_9). When a data transfer with memory cells is performed atthe first mode of operation, the data transfer unit connects bit lines,being equal in number to the first data bus, from among a plurality ofbit lines to the first data bus to transfer data. When a data transferwith memory cells is performed at the second mode of operation, the datatransfer unit connects bit lines, being equal in number to the seconddata bus, from among a plurality of bit lines to the second data bus totransfer data.

If the number of bit lines is n (n being a common multiple of p and qbeing a natural number, p>q), the first data bus is q, and the seconddata bus is q. If (n/p) address signals are received at the first modeof operation, the data transfer unit connects p bit lines to the p firstdata bus. If (n/q) address signals are received at the second mode ofoperation, the data transfer unit connects q bit lines to the seconddata bus.

Also, the NAND flash memory 10 comprises a memory array 101, a pagebuffer 82 configured to read data from the memory array 101 by the pageunit and to store read data read from the memory array 101, an ECCcircuit 107 configured to correct an error on the read data transferredfrom the page buffer 82 and to write the error-corrected data back inthe page buffer 82, and an IO pad (or, an interface unit) 106 configuredto output the read data written back in the page buffer 82. ECCBus isconnected to the ECC circuit 107, and DataBus is connected to the IO pad106.

In the NAND flash memory 10, the page buffer 82 stores write datareceived through the IO pad 106, and the ECC circuit 107 generatesparity data on the write data transferred from the page buffer 82. Theparity data and write data are written back in the page buffer.

By this, it is possible to control column coding, that is, addressesindependently by preparing a plurality of data buses (e.g., ECCBus andDataBus). In exemplary embodiments, it is possible to control addressesindependently by forming a data bus to be independent from input/outputlines of the page buffer 102 (e.g., IO_0 to IO_39), that is, a portiondirectly connected to the page buffer. Thus, the semiconductor memorydevice according to an embodiment of the inventive concepts obtains thefollowing effects.

(1) A high-speed operation is implemented by widening a bus width at thefirst mode of operation (e.g., the ECC mode). There is described such acase that when a column address is received once, 8-bit data istransferred to DataBus at the second mode of operation (e.g., the normalmode) and 20-bit data is transferred at the ECC mode. A bus width iseasily widened according to an input of Address_B, that is, columncoding to the page buffer 102. For example, if two column addresses areused for 1024 PB units, it is possible to transfer data with the ECCBusbeing widened a 512-bit bus width at the ECC mode. Also, it is possibleto form a data bus independent from a portion directly connected to thepage buffer and to control addresses independently. For this reason, ascompared with the case that data is transferred to an ECC circuit usinga part of the data bus like a conventional technique, a high-speed datatransfer is implemented. The reason is that there is not required acircuit (e.g., a first latch circuit 70 of a conventional example)associated with address control for separating a data transfer at thenormal mode and a data transfer at the ECC mode. In particular, in caseof a defective PB unit, since the PB control circuit 60 transfers fixeddata to the ECC circuit 107 through ECCBus, it is unnecessary totransfer data repaired through the column repair circuit 104 on ECCprocessing to the ECC circuit 107 through ECCBus. Also, it isunnecessary to dispose the column repair circuit 104 on ECCBus the buswidth of which is widened. For this reason, a time taken to transferdata from a page buffer to an ECC circuit at ECC processing is shortenedby a time taken for repair processing of the column repair circuit 104.Also, since it is unnecessary to widen a bus width of DataBus (e.g., asecond data bus) at ECC processing, an increase in a circuit size of thecolumn repair circuit 104 is suppressed.

(2) Freedom on address control and mapping is improved. At a normalmode, when 8-bit data is transferred using a column address, forexample, data of IO lines IO_0 to IO_7 is transferred to DataBus byproviding a selection signal Sel_A<0> to PB 4IO units 30_0 and 30_1. Inthis behalf, at an ECC mode, data on all addresses is transferred to theECC circuit in a lump by allocating an address independent from theselection signals Sel_B<0> and Sel_B<1> to the PB 4IO units 30_0 and30_1. For example, although normal data and parity data are assigned todifferent addresses of the selection signal Sel_A at a normal mode, theyare assigned to the same address of the selection signal Sel_B at theECC mode, and normal data and parity data are transferred to the ECCcircuit in a lump. Thus, address control at the second mode of operationand address control at the first mode of operation are independent fromeach other, and freedom of address mapping is high.

Also, at the normal mode, a column address is used with respect to fiveselection signals Sel_A<0> to Sel_A<4>. At the ECC mode, a columnaddress is used with respect to two selection signals Sel_B<0> andSel_B<1>. This means that although a column address has a value notbeing 2^(n) in case of the user specification of the normal mode, it iseasy to change an address space of the ECC mode to a unit space having avalue of 2^(n). By this, a code composition of the ECC circuit 107, forexample, a code length (e.g., optimization on code length composition incase of cumulative coding) may be decided with freedom, and optimalperformance is achieved.

(3) A design change is easily made. In case of designing a productincluding an ECC circuit, it is assumed that a product is a derivationproduct and a product not including an ECC circuit is separatelydesigned. In this case, data buses and column coding circuits associatedwith address control are independent with respect to the ECC mode andthe normal mode. By this, it is possible to separate a circuitassociated with the ECC mode and a circuit associated with the normalmode. Thus, it is easy to eliminate the circuit associated with the ECCmode. This means that a design change is easily made.

FIGS. 19A, 19B and 19C are diagrams for describing page data associatedwith a page buffer 102. FIGS. 20A through 2D are flow charts fordescribing an operation of a page buffer 102. In FIG. 19A, there areschematically illustrated a page buffer 120 a for main data (normaldata), a page buffer 102 b for column repair for main data (repair dataof normal data), a page buffer 102 c for ECC parity (parity data), and apage buffer 102 d for parity's column repair (repair data of paritydata). In FIG. 19A, numbers indicate PB units (e.g., a PB controlcircuit 60 and bit internal circuits 50_0 to 50_7 shown in FIGS. 15 and16) constituting the page buffers 102 a to 102 d.

The numbers are numbers of selection signals Sel_A indicating locationsof PB units, that is, Coding shown in FIG. 14B. that is, the page buffer102 a includes 256 PB units 0 to 255 for normal data, the page buffer102 b includes 8 PB units 256 to 263 for repair of normal data, the pagebuffer 102 c includes 36 PB units 264 to 299 for parity data, and thepage buffer 102 d includes 8 PB units 300 to 307 for repair of paritydata.

In FIG. 19B, there is illustrated an example in which when eight bitlines connected to a PB unit 1 of the page buffer 102 a or memory celltransistors connected to eight bit lines are defective, the PB unit 1 ofthe page buffer 102 a is replaced with a PB unit 256 of the page buffer102 b. Also, in FIG. 19B, there is illustrated an example in which wheneight bit lines connected to a PB unit 265 of the page buffer 102 c ormemory cell transistors connected to eight bit lines are defective, thePB unit 265 of the page buffer 102 c is replaced with a PB unit 300 ofthe page buffer 102 d. PB units 257 to 263 of the page buffer 102 bcorresponding to a slashed portion in FIG. 19B are unused PB units, sothat the PB units 257 to 263 are not selected by a column coding circuit103 under a control of a column repair circuit 104. That is, the PBunits 257 to 263 may be at an inactive state. PB units 301 to 307 of thepage buffer 102 d corresponding to a slashed portion in FIG. 19B areunused PB units, so that the PB units 301 to 307 are not selected by anECC column coding circuit 108 under a control of a parity column repaircircuit 105. That is, the PB units 301 to 307 may be at an inactivestate.

At a normal mode, since the PB unit 1 of the page buffer 102 a is notselected and the PB unit 256 replaced is selected by a selection signalSel_A, read data Data_Out_A (e.g., data read from the PB unit 1) isoutput to an I/O pad 106 through DataBus_(—)1, DataBus_(—)2, andDataBus_(—)3 (e.g., a second data bus). If write data is received fromthe I/O pad 106 at the normal mode, it is provided to the PB unit 255through DataBus_(—)3, DataBus_(—)2, and DataBus_(—)1 as the write dataData_A_In (data to be stored in the PB unit 1). As described above, aregion of a page buffer where a user may provide a column address isfrom the PB unit 0 to the PB unit 255. That is, the PB unit 256 to 263of the page buffer 102 b, the PB units 264 to 299 of the page buffer 102c, and the PB units 300 to 307 of the page buffer 102 d form a pagebuffer region that is inaccessible by a user.

The PB unit 1 of the page buffer 102 a is selected by a selection signalSel_B at an ECC mode, and read data Data_Out_B fixed to a low level or ahigh level is transferred to an ECC circuit 107 through ECCBus_(—)1 andECCBus_(—)2 (e.g., a first data bus) to be used for ECC processing.Also, the repaired PB unit 256 is selected by the selection signalSel_B, and read data Data_Out_B is transferred to the ECC circuit 107through ECCBus_(—)1, ECCBus_(—)2, and ECCBus_(—)3 to be used for ECCprocessing as read data of the PB unit 1 seen from the user. At the ECCmode, if the ECC processing is ended, data to be written back at the PBunit 1 is provided to the PB unit 255 through ECCBus_(—)3, ECCBus_(—)2,and ECCBus_(—)1 (e.g., a first data bus) as write data Data_A_In. Inaddition, data, corresponding to PB units 0 to 255, from amongECC-processed data may be provided to the external device as clear datathrough a data bus Data_A.

The PB unit 265 of the page buffer 102 c is selected by the selectionsignal Sel_B at the ECC mode, and read data Data_Out_B fixed to a lowlevel or a high level is transferred to a parity column repair circuit105 through ECCBus_(—)1 and ECCBus_(—)2 (e.g., data bus Data_B). Also,the repaired PB unit 300 is selected by the selection signal Sel_B, andread data Data_Out_B is transferred to the parity column repair circuit105 through ECCBus_(—)1 and ECCBus_(—)2 to repair processing. At the ECCmode, if the ECC processing is ended, data to be written back at the PBunit 265 is provided to the parity column repair circuit 105 throughECCBus_(—)3 for repair processing, and resultant data is then providedto the PB unit 300 through ECCBus_(—)2 and ECCBus_(—)1 (e.g., a firstdata bus) as write data Data_A_In. In addition, ECC-processed data isnot output to the external device through the data bus Data_A asdescribed above.

A data write operation to a memory cell transistor and a data readoperation from a memory cell transistor are described with reference toFIG. 20A through 20D. FIG. 20A shows a data write operation, FIG. 20Bshows a data read operation, FIG. 20C show an ECC encoding operation,and FIG. 20D shows an ECC decoding operation.

Data Write Operation

In step ST1, a user provides a NAND flash memory 10 with a predeterminedcommand (e.g., a write command), an address (here, indicating a columnaddress selecting a PB unit 1), and write data through an I/O pad 106.In step ST2, a repair of normal data is executed. More particular, acolumn coding circuit 103 selects a PB unit 256 instead of a PB unit 1under a control of a column repair circuit 104 such that the write datais stored in the PB unit 256.

After a time elapses, the method proceeds step ST6 when a mode is anormal mode (e.g., a second operation mode) where the user invokes aprogram execution command. In step ST6, programming is executed suchthat data is transferred to a memory cell transistor from a page bufferthrough a bit line. In case of an ECC mode (e.g., a first mode ofoperation), the method proceeds to step ST5 to execute an ECC encodingoperation as follows.

Here, FIG. 19C shows a code structure at ECC processing. A data unit isdata stored in PB units 0 to 263, and a parity unit (ECC unit) is datastored in PB units 264 to 299. Data to be written in the PB unit 1 isstored in the PB unit 256, and data stored in memory cell transistorsare read and stored in PB units 0 and 2 to 255 through connectedthereto. In step ST31, data stored in the PB units 0 to 263 is providedto an ECC circuit 107 through ECCBus_(—)1, ECCBus_(—)2, and ECCBus_(—)3(e.g., a first data bus).

As described above, at this time, fixed data (e.g., L data in case of aPB control circuit 60 shown in FIG. 15 or H data in case of a PB controlcircuit 60 shown in FIG. 16) is provided from the PB unit 1 to the ECCcircuit 107. Data that is data to be written in the PB unit but datawritten in the PB unit 256 is provided to the ECC circuit 107 from thePB unit 256. The ECC circuit 107 generates parity data through anencoding operation (ST32).

The ECC circuit 107 stores ECC-processed data in the PB units 0 to 263(ST33). At this time, an ECC coding circuit 108 selects a PB unit 300instead of a PB unit 265 under a control of a column repair circuit 105.By this, parity data to be written back in the PB unit 265 is stored inthe PB unit 300. At encoding, data is not written back to the PB units 0to 263. However, the same data may be written back. Parity data iswritten at PB units 264 to 307. A page buffer having an inactive stateas a slashed portion in FIG. 19B is not written by a circuit shown inFIG. 15 or 16.

Since data Data_i to be written at a memory cell is latched by a latchunit of each PB unit, a memory cell transistor is programmed (ST6). Datais iteratively provided to a memory cell from a latch unit of each PBunit until a program operation is passed (ST7). If the program operationis passed, the iterative process is ended (ST7—Yes). If the programoperation is not passed, the procedure goes to step ST6 for a programoperation until the program operation is passed (ST7—No).

Data Read Operation

A user provides a predetermined command (e.g., a read command) and anaddress (e.g., a column address selecting the PB unit 1) (ST11). Data ofa memory cell transistor is sensed by a latch unit of each PB unit andthe sensed data is latched on a connection node N1 of a bit internalcircuit show in FIG. 16 (ST12). Data_i is latched by the latch unit ofthe bit internal circuit (ST13). In case of a normal mode (e.g., asecond mode of operation), the procedure goes to step ST15 to end asensing operation. In case of an ECC mode (e.g., a first mode ofoperation), the procedure goes to step ST14 to perform an ECC decodingoperation as follows.

Data stored in PB units 0 to 299 is provided to the ECC circuit 107through ECCBus_(—)1, ECCBus_(—)2, and ECCBus_(—)3 (e.g., a first databus).

As described above, at this time, fixed data (e.g., L data in case of aPB control circuit 60 shown in FIG. 15 or H data in case of a PB controlcircuit 60 shown in FIG. 16) is provided from the PB unit 1 to the ECCcircuit 107. Also, data that is data to be written in the PB unit 1 butdata written in the PB unit 256 is provided to the ECC circuit 107 fromthe PB unit 256. Fixed data is provided from the PB unit 265 to the ECCcircuit 107. Also, parity data that is data to be written in the PB unit265 but data written in the PB unit 300 is provided to the ECC circuit107 from the PB unit 300. Also, parity data that is data to be writtenin the PB unit 265 but data written in the PB unit 300 is provided to aparity column repair circuit 105 from the PB unit 300 throughECCBus_(—)1 and ECCBus_(—)2. After a repair operation, resultant data isprovided to the ECC circuit 107 through ECCBus_(—)3. The ECC circuit 107corrects an error of data stored in the PB units 0 to 263 through adecoding operation, based on parity data (ST42).

The ECC circuit 107 stores ECC-processed data in the PB units 0 to 299(ST43). ECC-processed data (e.g., error-corrected data) is stored in thePB units 0 to 263. Since parity data units of PB units 264 to 307 arenot used by the user, ECC-processed data (e.g., error-corrected data) isnot stored in the PB units 264 to 307. However, it is possible to storeECC-processed data (e.g., error-corrected data) in the PB units 264 to307. The PB unit 300 is selected instead of the PB unit 265 under acontrol of a parity column repair circuit 105. By this, error-correctedparity data to be written back in the PB unit 265 is stored in the PBunit 300. A page buffer having an inactive state as a slashed portion inFIG. 19B is not written by a circuit shown in FIG. 15 or 16.

Since data Data_i to be written at a memory cell is latched by a latchunit of each PB unit shown in FIG. 17, a sensing operation is ended andit enters a readable state (ST15).

As a selection signal Sel_A is provided to the PB units 0 to 255, datastored therein is read through DataBus_(—)1, DataBus_(—)2, andDataBus_(—)3.

At this time, a column coding circuit 103 selects the PB unit 256instead of the PB unit 1 under a control of the column repair circuit104. The PB unit 256 outputs data that is data to be written at the PBunit 1 but data written at the PB unit 256. That is, a defect column isrepaired (ST16). As described above, write data written at memory celltransistors through the PB unit 1 according to a user's request iswritten at another memory cell after repairing. Also, an error of thewritten data is corrected and the error-corrected data is output fromthe I/O pad (ST17).

A semiconductor memory device of the inventive concepts comprisesECCBus_(—)1 to ECCBus_(—)3 (e.g., a first data bus), DataBus_(—)1 toDataBus_(—)3 (e.g., a second data bus) being different in number fromthe first data bus and independent from the first data bus, and a pagebuffer 102 (e.g., a data transfer unit). When a data transfer withmemory cells is performed at an ECC mode (e.g., a first mode ofoperation), the page buffer connects bit lines, being equal in number tothe first data bus, from among a plurality of bit lines to the firstdata bus to transfer data. When a data transfer with memory cells isperformed at a normal mode (e.g., a second mode of operation), the pagebuffer connects bit lines, being equal in number to the second data bus,from among a plurality of bit lines to the second data bus to transferdata. Also, the data transfer unit comprises a page buffer 102 a (e.g.,a first page buffer) that amplifies a voltage of a bit line connected toa normal memory cell and latches the amplified result, a page buffer 102b (e.g., a second page buffer) that is replaced together with a normalmemory cell and a bit line when the normal memory cell or the bit lineconnected to the first page buffer is defective, and a page buffer 102 c(e.g., a third page buffer) that amplifies a voltage of a bit lineconnected to a parity memory cell and latches the amplified result.Also, the second data bus is connected to the first and second pagebuffers, and the first data bus is connected to the first to third pagebuffers.

Also, the semiconductor memory device comprises a page buffer 102 (e.g.,a fourth page buffer) that is replaced together with a parity memorycell and a bit line when the parity memory cell or the bit lineconnected to the third page buffer is defective, a column repair circuit104 (e.g., a first repair circuit) that is connected to the second busand repairs a page buffer, connected to a defective memory cell or bitline, from among the first page buffer with the second page buffer, aparity column repair circuit 105 (e.g., a second repair circuit) that isconnected to the first bus and repairs a page buffer, connected to adefective memory cell or bit line, from among the third page buffer withthe fourth page buffer, and an ECC circuit 107 that is connected to thefirst data bus and corrects an error of output data of the first andsecond page buffers based on output data of the third and fourth pagebuffers.

Also, the semiconductor memory device comprises a PB control circuit 60that sets an output of a page, connected to a defective memory cell orbit line, from among the first page buffer, to fixed data.

Also, when a memory cell or a bit line is defective, the PB controlcircuit does not allow writing from the first data bus.

Also, in a semiconductor memory device of the inventive concepts, duringthe first mode of operation, it is viewed as input data of the ECCcircuit without a repair of a page buffer, corresponding to a defectivememory cell or bit line, from among the first page buffer and the secondpage buffer existing for a repair at the second mode of operation.

Also, If the number of bit lines is n (n being a common multiple of pand q being a natural number, p>q), the first data bus is q, and thesecond data bus is q. If (n/p) address signals are received at the firstmode of operation, the data transfer unit connects p bit lines to the pfirst data bus. If (n/q) address signals are received at the second modeof operation, the data transfer unit connects q bit lines to the seconddata bus. Although the number n of physical bit lines is not a commonmultiple of p and q, the remaining may be used as dummy bit lines.

With the inventive concepts, since it is easy to widen a bus width ofthe ECC bus (e.g., a first data bus) to the ECC circuit 107 (e.g., a buswidth to the ECC circuit being 300 bits), also, a repair circuit (e.g.,a column repair circuit 104) of a main data unit is unnecessary on theECC bus. For this reason, it is possible to implement a high-speed datatransfer at ECC processing. Also, since a size of a repair circuit ofthe main data unit is not increased unlike a conventional technique, anincrease in chip size is suppressed and a cost for fabrication islowered.

Also, in exemplary embodiments, there is described an embodiment wherethere is used a PCR repair system (e.g., a parity column repair circuit105) dedicated to a parity unit having a size smaller than that of arepair circuit of the main data unit. However, the inventive conceptsare not limited thereto. Only, the parity column repair circuit 105 isuseful to repair a defect of the parity unit. In the event that theparity column repair circuit 105 is not used, the error correctioncapacity is damaged. The reason is that an error is corrected byprobability of 50% (0 or 1) per bit of column. In this behalf, asdescribed above, the ECC correction capacity is improved by repairing adefect of the parity unit using the parity column repair circuit 105.

Third Embodiment

There is provided a semiconductor memory device configured to prevent anincrease in size of a repair circuit for replacing a page bufferassociated with a defective memory cell or a defective bit line with adefect-free page buffer and to implement a high-speed data transfer ofan ECC circuit. A data transfer unit comprises a page buffer 102 a thatamplifies a voltage of a bit line connected to a normal memory cell andlatches the amplified result, a page buffer 102 b that is replacedtogether with a normal memory cell and a bit line when the normal memorycell or the bit line connected to the page buffer 102 a is defective,and a page buffer 102 c that amplifies a voltage of a bit line connectedto a parity normal memory cell and latches the amplified result.DataBus_(—)1 is connected to the page buffers 102 a and 102 b, andDataBus_(—)2 is connected to the page buffers 102 a, 102 b, and 102 c.

In a conventional semiconductor memory device, a so-called data busconnecting an I/O pad (e.g., an interface unit) and a memory array isformed of a single bus when seen from a sense amplifier (referred to asa page buffer in a flash memory).

FIG. 44 is a block diagram schematically illustrating a conventionalNAND flash memory. The NAND flash memory 80 shown in FIG. 44 comprises amemory array 101, a page buffer 82, a column coding circuit 83, anaddress control circuit 85, and an I/O pad 106. The memory array 101 isconfigured to include a plurality of memory cell transistors. Each ofthe memory cell transistors stores 1-bit data. A plurality of memorycell transistors of the memory array 101 connected to the same word lineforms a page. Data is written at and read from memory cell transistorsin a page at the same time.

The page buffer 82 is configured to store data corresponding to a pageof the memory array 101. FIG. 45 is a diagram schematically illustratinga page buffer unit of a page buffer 82. FIG. 46 is a circuit diagram ofa conventional page buffer unit. The page buffer 82 includes a pagebuffer unit shown in FIG. 45 in plurality. The page buffer unitcomprises bit circuits 51_0 a to 51_7 a that are respectively connectedto bit lines and store data read from memory cells through the bit linesor data to be written at memory cells through the bit lines.

A multiplexer 52 _(—) b receives a column address (Sub BL Coding) from acolumn coding circuit 83 shown in FIG. 44 and selects one of the bitcircuits 51_0 a to 51_7 a based on the column address (indicating DIO<i>in FIG. 46). That is, the multiplexer 52 _(—) b connects one of eightbit lines to a PB control circuit 83_1.

The PB control circuit (or, a transfer unit) 83_1 receives a columnaddress Coding (indicating a selection signal Sel in FIG. 46) from thecolumn coding circuit 83 shown in FIG. 44 and connects a bit circuitselected by the multiplexer 52 _(—) b to a peripheral circuit through adata bus.

With the above-described structure, each memory cell transistor in apage is connected to a bit circuit of the page buffer 82 through a bitline. One, selected by a column address, from among the bit lines isconnected to the data bus such that data is written at or read from amemory cell.

Returning to FIG. 44, the column coding circuit 83 generates columnaddress signals (Sub BL Coding and Coding shown in FIG. 45) based on acolumn address received from an address control circuit 85. The columncoding circuit 83 selects a page buffer unit in the page buffer 82corresponding to the column address. Thereby, data is written at amemory cell transistor through the I/O pad 106, the data bus, the bitcircuit and the bit line. Also, data read from a memory cell is outputto the exterior of the I/O pad 106 through the bit line, the bit circuitand the data bus.

The data bus is a wiring used to input and output data between the pagebuffer 82 and the I/O pad 106 and is formed of 8 or 16 lines. The I/Opad (an interface unit) 106 is an external terminal for datainput/output between the NAND flash memory 80 and the exterior.

In a NAND flash memory, as a storage characteristic of a memory element(a memory cell transistor) disappears during data preservation due todeterioration of a tunnel oxide film caused by a plurality of writeoperations, an error bit generation rate (an error rate) increases. Inparticular, in the NAND flash memory, an error rate increases inproportion to an increase in storage capacity of a memory cell, that is,scale-down of a fabrication process. For this reason, redundancy data(parity data) of an error correcting code (ECC) is added to data to bewritten, and the redundancy data is together written in a flash memoryas a data stream. During a read operation, data is corrected using theredundancy data of the error correcting code. When an error bit isgenerated, data is corrected. The ECC may be processed outside or insidethe NAND flash memory.

In the event that the ECC is processed outside the NAND flash memory 80,a memory controller connected through the I/O pad 106 processes the ECC.Meanwhile, in the event that the ECC is processed inside the NAND flashmemory 80, the NAND flash memory 80 necessitates an error detecting andcorrecting circuit (an ECC unit). FIG. 47 is a block diagramschematically illustrating a NAND flash memory including an ECC circuit.In FIG. 47, constituent elements that are the same as those in FIG. 44are marked by the same reference numerals, and a description thereof isthus omitted. A NAND flash memory 90 shown in FIG. 47 further comprisesan ECC circuit 87 as compared with a NAND flash memory 80 shown in FIG.44. The ECC circuit 87 is connected to a data bus.

When data is read from memory cell transistors, the ECC circuit 87sequentially receives data (including normal data and redundancy data)corresponding to a page of memory cell transistors and to be stored inthe page buffer 82 through the data bus, and determines whether an errorexists at each bit, based on the page data. The ECC circuit 87 correctsdata when an error exists, and sequentially writes corrected data backin each bit circuit of the page buffer 82 through the data bus.Afterwards, the address control circuit 85 provides a column address tothe column coding circuit 83, the column coding circuit 83 selects apage buffer unit of the page buffer 82, and the corrected data stored inthe page buffer 82 is read from the I/O pad 106.

When data is written at memory cell transistors, a page of normal datais provided from the page buffer 82 to the ECC circuit 87 and new datais simultaneously provided to the ECC circuit 87 from the I/O pad 106.Redundancy data is generated based on the page of normal data includingthe new data, the normal data and the redundancy data are written at thepage buffer 82, and data is written at memory cell transistors through awrite (program) operation.

In the NAND flash memory 90, when the ECC is processed, data is notoutput to the exterior using a bus width of the I/O pad 106 at a dataread mode. For this reason, a time necessitates to process the ECC. Toreduce a time taken to process the ECC, such a manner that a bus widthis widened at processing of the ECC may be considered. For example, in apatent reference 1(JP Publication Number 2012-128921), there isdisclosed a semiconductor memory device including a transfer unit thatperforms a data transfer between a page buffer and an ECC circuit usinga first data bus at a first mode of operation and performs a datatransfer using a part of the first data bus at a second mode ofoperation where the ECC is not processed.

FIG. 48 is a block diagram schematically illustrating another example ofa NAND flash memory including an ECC circuit. FIG. 48 shows a transferunit 17 disclosed in FIG. 26 of the aforementioned patent reference 1.In FIG. 48, modes of operation indicated by arrows are respectivelyreferred to as a first mode of operation and a second mode of operation.For ease of description, page buffers respectively corresponding to 8bits are marked by reference numerals 12_1 to 12_8, respectively. InFIG. 48, a box including a first latch circuit 70, a second latchcircuit 71 (including 71A and 71B), and a third latch circuit 72indicates an 8-bit latch circuit.

Below, an operation of the transfer unit 17 when a data read operationis performed will be described. The transfer unit 17 transfers read datafrom the page buffers 12_1 to 12_8 to latch circuits 71_1 to 70_8through a data bus IO/IOn<63:0> during either one of a first mode ofoperation using an ECC unit 20 and a second mode of operation not usingthe ECC unit 20. Here, the latch circuit 70_1 is connected to the databus IO/IOn<7:0>, the latch circuit 70_2 is connected to the data busIO/IOn<15:8>, the latch circuit 70_3 is connected to the data busIO/IOn<23:16>, and the latch circuit 70_4 is connected to the data busIO/IOn<31:24>. The latch circuit 70_5 is connected to the data busIO/IOn<39:32>, the latch circuit 70_6 is connected to the data busIO/IOn<47:40>, the latch circuit 70_7 is connected to the data busIO/IOn<55:48>, and the latch circuit 70_8 is connected to the data busIO/IOn<63:56>.

At the second mode of operation, a column address is provided to thelatch circuits 70_1 to 70_8 four times such that 64-bit data supplied tothe latch circuits 70_1 to 70_8 is output to an 8-bit data busOUTLLn<7:0> and an 8-bit data bus OUTLLn<15:8>. Here, column addressessupplied four times are called as follows. That is, column addressessupplied to the latch circuit 70_1 to 70_4 is referred to as columnaddresses CA1 to CA4. That is, the column addresses CA1 to CA4 aresequentially supplied to the latch circuit 70_1 to 70_4, so that each of8-bit data stored in the latch circuit 70_1, 8-bit data stored in thelatch circuit 70_2, 8-bit data stored in the latch circuit 70_3, and8-bit data stored in the latch circuit 70_4 is transferred to the latchcircuit 71_B1 through the 8-bit data bus OUTLLn<7:0>.

Also, the column addresses CA1 to CA4 are sequentially supplied to thelatch circuit 70_5 to 70_8, so that each of 8-bit data stored in thelatch circuit 70_5, 8-bit data stored in the latch circuit 70_6, 8-bitdata stored in the latch circuit 70_7, and 8-bit data stored in thelatch circuit 70_8 is transferred to the latch circuit 71B_2 through the8-bit data bus OUTLLn<15:8>.

At the first mode of operation, a bus width is doubled to transfer dataof the latch circuits 70_1 to 70_8 to the ECC unit 20. That is, a databus OUTLLn<23:16> and a data bus OUTLLn<31:24> are installed to besubstantially the same as the data buses OUTLLn<7:0> and OUTLLn<15:8>.With the above description, at the first mode of operation, the latchcircuits 70_1 to 70_8 transfer stored data to the latch circuits 71A_1to 71A_4 when the column addresses CA1 to CA4 are received. The columnaddresses CA1 and CA3 are first supplied to the latch circuits 70_1 to70_8, and the column addresses CA2 and CA4 are then supplied to thelatch circuits 70_1 to 70_8.

First, when the column addresses CA1 and CA3 are supplied at the sametime, the latch circuits 70_1, 70_3, 70_5, and 70_7 transfer data. Thelatch circuit 70_1 transfers 8-bit data to the data bus OUTLLn<23:16> inresponse to the column address CA1 so as to be transferred to the latchcircuit 71A_3. The latch circuit 70_3 transfers 8-bit data to the databus OUTLLn<7:0> in response to the column address CA3 so as to betransferred to the latch circuit 71A_1. The latch circuit 70_5 transfers8-bit data to the data bus OUTLLn<15:8> in response to the columnaddress CA1 so as to be transferred to the latch circuit 71A_2. Thelatch circuit 70_7 transfers 8-bit data to the data bus OUTLLn<31:24> inresponse to the column address CA3 so as to be transferred to the latchcircuit 71A_4.

When there are simultaneously received the column addresses CA2 and CA4following the column addresses CA1 and CA3, the latch circuits 70_2,70_4, 70_6, and 70_8 transfer data. The latch circuit 70_2 transfers8-bit data to the data bus OUTLLn<23:16> in response to the columnaddress CA2 so as to be transferred to the latch circuit 71A_3. Thelatch circuit 70_4 transfers 8-bit data to the data bus OUTLLn<7:0> inresponse to the column address CA4 so as to be transferred to the latchcircuit 71A_1. The latch circuit 70_6 transfers 8-bit data to the databus OUTLLn<15:8> in response to the column address CA2 so as to betransferred to the latch circuit 71A_1. The latch circuit 70_8 transfers8-bit data to the data bus OUTLLn<31:24> in response to the columnaddress CA4 so as to be transferred to the latch circuit 71A_4.

In the first mode of operation, the transfer unit 17 includes the firstlatch circuit 70 to latch data (e.g., 64-bit data of memory celltransistors) output from the page buffer 12 using the data busIO/IOn<63:0> operating at the second mode of operation. As the number ofcolumn addresses supplied at the second mode of operation is set to betwo times more than the number of column addresses supplied at the firstmode of operation, the transfer unit 17 transfers data to the next-stagelatch circuits 71A_1 to 71A_4 using a part of the data bus used at thesecond mode of operation.

It is possible to output data in high speed by using a data bus for thesecond mode of operation in common and widening a bus width at the firstmode of operation. For this reason, a delay caused to operate a circuit(e.g., the latch circuit 70) for switching the second mode of operation(i.e., a normal mode) and the first mode of operation (i.e., an ECCmode) arises. As described above, at the ECC mode, an address decided toan address of a normal mode is supplied such that data is output to abus the width of which is widened. A high-speed data transfer is delayedby a time needed for processing.

Also, when data is transferred, since an address of data transferred toa data bus is decided using an address of a normal mode, it isimpossible to transfer data of an address selected by a user at the ECCmode. For example, referring to the above description, when all columnaddresses CA1 to CA4 are simultaneously selected, data of IO/IOn<63:32>or IO/IOn<31:0> is not transferred to the ECC circuit at the same time.In a conventional technique, when data is transferred, addresses are notcontrolled independently with respect to two modes of operation. Thatis, freedom on address control is low.

Further, in the event that a design of a NAND flash memory includingsuch an ECC circuit is changed to a design of a NAND flash memory 80(refer to FIG. 44) not including the ECC circuit, a design change ismade to delete a function of the first mode of operation on the latchcircuit 70 (e.g., to prevent data corresponding to two column addressesfrom being output at the same time). A design change is made such thatdata corresponding to two column addresses are prevented from beingoutput at the same time. This is achieved through a design change of anaddress control circuit. In a conventional technique, a part of a databus is shared with respect to the first mode of operation and the secondmode of operation. For this reason, a design is complicated when adesign change is made to delete an ECC function.

Also, in a conventional structure, a product (e.g., a NAND flash memory)has a first mode of operation and a second mode of operation. Beforeshipment, it is impossible to test each mode of operation under such acondition that a product (e.g., Pure NAND) including the second mode ofoperation and a product (e.g., EM NAND) including the first mode ofoperation are switched in operation. Therefore, the Pure NAND and the EMNAND are fabricated independently, and are tested before shipment. Or,inventory control is made according to an order. For this reason, it isdifficult to improve productivity.

In the event that a bus width used at the first mode of operation iswidened to a bus width used at the second mode of operation, ahigh-speed data transfer is achieved and freedom on address control isimproved. The effects are achieved through a transfer unit of asemiconductor memory device according to the inventive concepts.

A semiconductor memory device comprises a first data bus; a second databus being different in number from the first data bus and independentfrom the first data bus; and a data transfer unit, wherein when a datatransfer with memory cells is performed at a first mode of operation,the data transfer unit connects bit lines, being equal in number to thefirst data bus, from among a plurality of bit lines to the first databus to transfer data; wherein when a data transfer with memory cells isperformed at a second mode of operation, the data transfer unit connectsbit lines, being equal in number to the second data bus, from among theplurality of bit lines to the second data bus to transfer data, whereinthe data transfer unit comprises a first page buffer which latches dataof a bit line connected to a normal memory cell; and a second pagebuffer which latches data of a bit line connected to a parity memorycell, wherein the first data bus and the second data bus are connectedto the first page buffer and the second page buffer, wherein thesemiconductor memory device further comprises an ECC circuit which isconnected to the first data bus and corrects an error of output data ofthe first page buffer based on output data of the second page buffer,wherein the first mode of operation is a mode where the first pagebuffer is accessed and also is a mode of operation for execution of ECCprocessing where at a data write operation, the ECC circuit generatesparity data based on output data of the first page buffer and writes theparity data at the second page buffer and, at a data read operation, theECC circuit corrects an error of data of the first page buffer based onparity data of the second page buffer and writes the corrected data backin the first page buffer; wherein the second mode of operation is a modeof operation where the ECC processing is not executed and the secondpage buffer is not accessed and the first page buffer is accessed, andwherein to select and execute one of the first mode of operation and thesecond mode of operation is electrically switchable.

In exemplary embodiments, the second page buffer is accessed through thesecond data bus at the second mode of operation.

In exemplary embodiments the semiconductor memory device furthercomprises a mask circuit which outputs fixed data instead of data outputto an external device through the second data bus when the second pagebuffer is accessed at the second mode of operation.

The semiconductor memory device further comprises a third page bufferwhich is connected to the first and second data buses and is replacedtogether with a normal memory cell and a bit line when a normal memorycell or a bit line connected to the first page buffer is defective; afourth page buffer which is connected to the first and second data busesand is replaced together with a parity memory cell and a bit line when aparity memory cell or a bit line connected to the second page buffer isdefective; a first repair circuit which is connected to the second databus and replaces a page buffer, associated with a defective memory cellor bit line, of the first page buffer with the third page buffer at thesecond mode of operation; and a second repair circuit which is connectedto the first data bus and replaces a page buffer, associated with adefective memory cell or bit line, of the second page buffer with thefourth page buffer.

In exemplary embodiments, at the second mode of operation, the firstrepair circuit a page buffer, associated with a defective memory cell orbit line, of the second page buffer with the fourth page buffer.

In exemplary embodiments, the first repair circuit stores a columnaddress indicating a location of a page buffer to repair a page buffer,associated with a defective memory cell or bit line, of the first pagebuffer and selects a page buffer to be replaced by the stored columnaddress. The second repair circuit stores a column address indicating alocation of a page buffer to repair a page buffer, associated with adefective memory cell or bit line, of the second page buffer and selectsa page buffer to be replaced by the stored column address. Thesemiconductor memory device further comprises a bit conversion circuitwhich converts a column address the first repair circuit stores into acolumn address the second repair circuit stores.

In exemplary embodiments, the third page buffer and the fourth pagebuffer are selected by the first repair circuit and the second repaircircuit, based on a switching signal indicating whether thesemiconductor memory device operates at either one of the first andsecond modes of operation.

In exemplary embodiments, the semiconductor memory device furthercomprises a page buffer control circuit which outputs fixed data as anoutput of a page buffer, associated with a defective memory cell or bitline, from among the first to fourth page buffers. The page buffercontrol circuit does not allow a write operation from the first data buswhen a memory cell or a bit line is defective.

In exemplary embodiments, when the number of bit lines is n (n being acommon multiple of p and q being a natural number, p>q), the first databus is q, and the second data bus is q. If (n/p) address signals arereceived at the first mode of operation, the data transfer unit connectsp bit lines to the p first data bus. If (n/q) address signals arereceived at the second mode of operation, the data transfer unitconnects q bit lines to the second data bus.

A semiconductor memory device comprises a first data bus; a second databus being different in number from the first data bus and independentfrom the first data bus; and a data transfer unit. When a data transferwith memory cells is performed at a first mode of operation, the datatransfer unit connects bit lines, being equal in number to the firstdata bus, from among a plurality of bit lines to the first data bus totransfer data. When a data transfer with memory cells is performed at asecond mode of operation, the data transfer unit connects bit lines,being equal in number to the second data bus, from among the pluralityof bit lines to the second data bus to transfer data.

By this, a data bus connected to an output of a page buffer isindividually prepared for the first mode of operation (e.g., an ECCmode) and the second mode of operation (e.g., a normal mode). Thus, whendata is transferred to an ECC circuit at the first mode of operationlike a conventional technique, data does not pass through an unnecessarycircuit. Thus, data is transferred in high speed by widening a bus widthfrom a second data bus to a first data bus.

Also, in the transfer unit, a data bus used at the first mode ofoperation and a data bus used at the second mode of operation areindependent from an output portion of a page buffer, and an addresssupplied at a data transfer of the first mode of operation isindependent from an address supplied at a data transfer of the secondmode of operation. Thus, freedom on address control and freedom onaddress mapping are improved. For example, in the event that normal dataand parity data are transferred at the second mode of operation, theircolumn addresses are different from each other. The reason is that areaswhere both data is stored are physically spaced apart from each other.Therefore, at the second mode of operation, the normal data is readusing its column address, and the parity data is then read using itscolumn address. However, at the first mode of operation, data istransferred with a bus width being widened. Thus, address control andaddress mapping are made such that the normal data and the parity dataare simultaneously read to an ECC circuit using a column address.

Since a data bus used at the first mode of operation and a data bus usedat the second mode of operation are prepared independently from anoutput portion of a page, it is easy to eliminate an ECC function (e.g.,an ECC circuit) including a first data bus used at the first mode ofoperation. In this case, a design change is easily made.

A semiconductor memory device of the inventive concepts has the firstmode of operation and the second mode of operation and electricallyswitches operations. Before shipment, each mode of operation is testedunder such a condition that a product (e.g., Pure NAND) including thesecond mode of operation and a product (e.g., EM NAND) including thefirst mode of operation are switched in operation. Therefore, sinceinventory control is easily made according to an order, productivity isimproved.

FIG. 24 is a block diagram schematically illustrating a NAND flashmemory according to an embodiment of the inventive concepts. Referringto FIG. 24, a NAND flash memory 10 comprises a memory array 101, a pagebuffer 102, a column coding circuit 103, a main column repairmultiplexer (a column repair circuit) 104, a parity column repaircircuit (Parity CRMUX) 105, an ECC column coding circuit 108, an I/O pad106, an ECC engine (or, an ECC circuit) 107 a, and a randomize mixer (arandomizer) 107 b. Hereinafter, the ECC circuit 107 a and the randomizer107 b are referred to as a randomizer and ECC circuit 107.

In FIG. 24, DataBus_(—)1, DataBus_(—)2, and DataBus_(—)3 (a second databus) are lines through which data is exchanged between a page buffer 82and the I/O pad 106. Below, such lines are referred to as Data_Bus. TheI/O pad (an interface unit) 106 is an external terminal for datainput/output between the NAND flash memory 10 and a NAND controllercontrolling the NAND flash memory 10. Also, ECCBus_(—)1, ECCBus_(—)2,ECCBus_(—)3 (a first data bus) are lines through which data is exchangedbetween the page buffer 82 and the randomizer and ECC circuit 107.Below, such lines are referred to as ECC_Bus.

The memory array 101 is configured to include a plurality of memory celltransistors. Each of the memory cell transistors stores 1-bit data. Aplurality of memory cell transistors of the memory array 101 connectedto the same word line forms a page. Data is written at and read frommemory cell transistors in a page at the same time.

The NAND flash memory 10 includes a column coding circuit 103 and an ECCcoding circuit 108. A column address is independently provided to thecolumn coding circuit 103 or the ECC column coding circuit 108. Thecolumn coding circuit 103 and the ECC column coding circuit 108 output aselection signal Sel_A or a selection signal Sel_B to a PB controlcircuit 60 of the page buffer 102 to connect an output of a page bufferto either ECCBus_(—)1 or DataBus_(—)1 from a portion (e.g., a portionformed of a multiplexer 52 _(—) b and a PB control circuit 83_1 shown inFIG. 27B) directly connected to the page buffer 102.

The column coding circuit 83 generates column address signals (Sub BLCoding and Coding shown in FIG. 27B) based on a column address receivedfrom an address control circuit (not shown). The column coding circuit83 selects a page buffer unit in the page buffer 102 corresponding tothe column address. Thereby, data is written at a memory cell transistorthrough the I/O pad 106, data buses Data_Bus_(—)3, Data Bus_(—)2, andData_Bus_(—)1, the bit circuit and the bit line. Also, data read from amemory cell is output to the exterior of the I/O pad 106 through the bitline, the bit circuit and the data buses Data_Bus_(—)1, Data_Bus_(—)2,and Data Bus_(—)3.

In particular, the ECC column coding circuit 108 receives a columnaddress (hereinafter, marked by Address B) from an ECC circuit 107 a andoutputs the selection signal Sel_B to a PB control circuit 60independently from a column address provided to the column codingcircuit 103 from an address control circuit (not shown). In this case,an output of the page buffer 102 is connected to ECCBus_(—)1. By this,address control is separately executed when an output of the page buffer102 is connected to ECCBus_(—)1 or Data_Bus_(—)1.

In a conventional NAND flash memory, an output (a data bus)(hereinafter, referred to as an IO bus for distinction) of a page bufferis shared at a first mode of operation and a second mode of operation.In the NAND flash memory 10, the IO bus being an output of the pagebuffer is independently prepared without sharing at the first mode ofoperation and the second mode of operation.

By this, a path between an output of a page buffer and the randomizerand ECC circuit 107 does not need a circuit influencing a high-speeddata transfer of the column repair circuit 104. That is, it is possibleto transfer data in high speed. Also, a second data bus is set to a buswidth to correspond to the conventional repair efficiency. By this,since the size of the column repair circuit 104 is not increased, anincrease in chip size is suppressed. In the event that a design of theNAND flash memory 10 is changed to a design of a NAND flash memory notincluding an ECC circuit, it is possible to eliminate the ECC columncoding circuit 108, the parity column repair circuit 105, the buses ECCBus_(—)1 to ECC Bus_(—)3, and the randomizer and ECC circuit 107. Thatis, a design change is easily made.

The page buffer 102 is configured to store data corresponding to a pageof the memory array 101. The page buffer 102, as shown in FIG. 24,comprises PB (Page Buffer) (hereinafter, referred to as a page buffer102 a), PB_CR (hereinafter, referred to as a page buffer 102 b),PB_Parity (hereinafter, referred to as a page buffer 102 c), and PB_PCR(hereinafter, referred to as a page buffer 102 d). The page buffer 102 ais a page buffer (e.g., a first page buffer) that amplifies a voltage ofa bit line connected to a normal memory cell and latches the amplifiedresult. When the selection signal Sel_A is received from the columncoding circuit 103 at a data read operation of a normal mode (e.g., asecond mode of operation), the page buffer 102 a outputs the amplifiedresult to the I/O pad 106 through DataBus_(—)1, DataBus_(—)2, andDataBus_(—)3 (e.g., a second data bus) as read data Data_Out_A.Meanwhile, when the selection signal Sel_B is received from the ECCcolumn coding circuit 108 at a data read operation of an ECC mode (e.g.,a first mode of operation), the page buffer 102 a outputs the amplifiedresult to the randomizer and ECC circuit 107 through ECCBus_(—)1,ECCBus_(—)2, and ECCBus_(—)3 (e.g., a first data bus) as read dataData_Out_B.

When the selection signal Sel_A is received from the column codingcircuit 103 at a data write operation of the normal mode, the pagebuffer 102 a receives write data provided from the I/O pad 106 throughData_Bus_(—)3, Data Bus_(—)2, and Data_Bus_(—)1 as write data Data_In_A.Meanwhile, when the selection signal Sel_B is received from the ECCcolumn coding circuit 108 at a data write operation of the ECC mode, thepage buffer 102 a receives a result of ECC processing of the ECC circuit107 a of the randomizer and ECC circuit 107 through ECCBus_(—)3,ECCBus_(—)2, and ECCBus_(—)1 as write data Data_In_B.

The page buffer 102 b is a page buffer (e.g., a third page buffer) thatis replaced together with a normal memory cell and a bit line when thenormal memory cell or the bit line connected to the page buffer 102 a isdefective. That is, in the event that one of page buffer unitsconstituting the page buffer 102 a is abnormal, the abnormal page bufferunit is repaired with one of page buffer units in the page buffer 102 b.The page buffer 102 b operates substantially the same as that of thepage buffer 102 a, and a description thereof is thus omitted.

The column repair circuit 104 is a circuit for replacing a page bufferunit of the page buffer 102 a with a page buffer unit of the page buffer102 b. If a column address (e.g., a selection signal Sel_A) forselecting an abnormal page buffer unit of the page buffer 102 a isprovided to the column coding circuit 103, the column coding circuit 103controls to select a page buffer unit of the page buffer 102 b.

The page buffer 102 c is a page buffer (e.g., a second page buffer) thatamplifies a voltage of a bit line connected to a parity memory cell(formed of a memory cell transistor for ECC processing configured thesame as a normal memory cell) and latches the amplified result. Inaddition, parity data a parity memory cell stores is not output to theexterior through the I/O pad 106 at a normal mode. Meanwhile, if aselection signal Sel_B is received from the ECC column coding circuit108 at a data read operation of the ECC mode, the page buffer 102 coutputs the amplified result to the ECC circuit 107 through ECCBus_(—)1,ECCBus_(—)2, and ECCBus_(—)3 as read data Data_Out_B.

Also, parity data a parity memory cell stores is not received from theexterior through the I/O pad 106 at the normal mode. Meanwhile, if theselection signal Sel_B is received from the ECC column coding circuit108 at a data write operation of the ECC mode, the page buffer 102 creceives parity data being a result of ECC processing of the ECC circuit107 through ECCBus_(—)3, ECCBus_(—)2, and ECCBus_(—)1 as write dataData_Out_B.

The page buffer 102 d is a page buffer (e.g., a fourth page buffer) thatis replaced together with a parity memory cell and a bit line when theparity memory cell or the bit line connected to the page buffer 102 c isabnormal. That is, in the event that one of page buffer unitsconstituting the page buffer 102 c is abnormal, the abnormal page bufferunit is repaired with one of page buffer units in the page buffer 102 d.The page buffer 102 d operates substantially the same as that of thepage buffer 102 c, and a description thereof is thus omitted.

The parity column repair circuit 105 is a circuit for replacing a pagebuffer unit of the page buffer 102 c with a page buffer unit of the pagebuffer 102 d. If a column address (e.g., a selection signal Sel_B) forselecting an abnormal page buffer unit of the page buffer 102 c isprovided to the ECC column coding circuit 108, the ECC column codingcircuit 108 controls to select a page buffer unit of the page buffer 102d.

FIG. 25 is a block diagram schematically illustrating a randomizer andECC circuit 107. In exemplary embodiments, a randomizer and ECC circuit107 is describing an ECC circuit using a Galois field operationrepresented as BCH code (Bose-Chaudhuri Hocquenghem code). Hamming code,Reed-Solomon code, etc. may be used as the BCH code.

Also, an error correction operation is performed by a 511-bit unit usingthe BCH code capable of correcting four bits of the 511-bit unit. Amongthe randomizer and ECC circuit 107, an ECC circuit 107 a shown in FIG.24 is configured to include a decoder unit for decoding data and anencoder unit for generating parity data. The decoder unit of the ECCcircuit 107 a is configured to include a syndrome calculation circuit31, an error-coefficient calculation circuit 32, and a chien searchcircuit 33. At a data read operation of an ECC mode, the syndromecalculation circuit 31 receives data read from memory cells by a pagebuffer 102 as code data Load Data<510:0>, for example, by a sector unit.

The syndrome calculation circuit 31 calculates a syndrome by dividingthe code data Load Data<510:0> by an independent minimal polynomial. Thenumber of independent minimal polynomials used as the BCH code capableof correcting a 4-bit data error is 4. The syndrome calculation circuit31 includes four syndrome calculation units respectively correspondingto four independent minimal polynomials. The syndrome calculation unitscalculate syndromes (e.g., S1, S3, S5, and S7), respectively.

The error-coefficient calculation circuit 32 uses the syndromes S1, S3,S5, and S7 to calculate coefficients (e.g., e4, e3, e2, e1, and e0) ofan error location search equation every sector. The coefficients e4, e3,e2, e1, and e0 are coefficients of an error location search equationΛ(x) (=e4×4+e3×3+e2×2+e1×1+e0). The error location search equation Λ(x)is used by the chien search circuit 33 to determine whether an errorexists at data read from the page buffer 102 every sector.

The chien search circuit 33 checks whether the error location searchequation Λ(x) is ‘0’, by plugging an address indicating a location ofthe code data Load Data<510:0> as a plug-in value x in the errorlocation search equation Λ(x) using coefficients (e.g., coefficients e0to e4 of the error location search equation) calculated by theerror-coefficient calculation circuit 32. The chien search circuit 33outputs an error detection signal EP<510:0> being a signal indicating anerror position according to the checking result. In the error detectionsignal EP<510:0>, bits, corresponding to an erroneous bit, from amongcode data Load Data<510:0> have ‘1’, and bits, corresponding to anerror-free bit, from among code data Load Data<510:0> have ‘0’

At a data read operation of an ECC mode of the NAND flash memory 10, therandomizer 107 b is supplied with code data Load Data<510:0> of the pagebuffer 102 at a location indicated by a column address when the ECCcolumn coding circuit 108 provides a selection signal Sel_B (e.g., thecolumn address) to the page buffer 102. The randomizer 107 b obtainserror-free data by EXORing the code data Load Data<510:0> and the errordetection signal EP<510:0> such that an error-free bit is not invertedand an erroneous bit is inverted.

Also, the randomizer 107 b EXORs the error-free data and a random seedRS<510:0> generated by a random seed generation circuit (not shown),that is, de-randomizes. The randomizer 107 b restores the code data LoadData<510:0> to a state before encoding. The randomizer 107 b writes therestored data Store Data<510:0> at the page buffer 102.

A data flow at a data read operation (decoding and de-randomizing) of anECC mode is illustrated by a solid line (indicating a data flow atdecoding) and an alternate long and short dash line (indicating a commondata flow of encoding and decoding). Also, at a data read operation ofthe ECC mode, code data Store Data being data to be written at the pagebuffer 102 is expressed by an equation: Store Data=(LoadData)XOR(EP)XOR(RS). In the equation, ‘Load Data’ indicates code databeing data read from the page buffer 102, ‘EP’ indicates an errordetection signal, and ‘RS’ indicates a random seed. Also, at a data readoperation of a normal mode, data of the code data Store Data except forparity data is output to the exterior through the I/O pad by providing aselection signal Sel_A (e.g., a column address) from the column codingcircuit 103 to the page buffer 102.

An encoder unit 40 of the ECC circuit 107 a has a parity generationcircuit 41. The parity generation circuit 41 generates parity data bydividing randomized data provided from the randomizer 107 b bygeneration polynomial and outputs the parity data to the page buffer 102(e.g., a page buffer 102 c).

At a data write operation of an ECC mode (e.g., encoding andrandomizing), the randomizer 107 b randomizes code data Load Data<510:0>provided from the page buffer 102. At this time, in the randomizer 107b, the error detection signal EP<510:0> is fixed data (all ‘0’), thatEP<510:0>=0. The randomizer 107 b executes an exclusive OR operation onthe code data Load Data<510:0>, the random seed RS<510:0> and the errordetection signal EP<510:0> to generate code data Store Data to be outputto the parity generation circuit 41.

The code data Store Data being data written at the parity generationcircuit 41 is expressed, at decoding, by an equation: Store Data=(LoadData)XOR(EP)XOR(RS). In the equation, ‘Load Data’ indicates code databeing data read from the page buffer 102, ‘EP’ indicates an errordetection signal, and ‘RS’ indicates a random seed. Also, the paritygeneration circuit 41 generates parity data from the code data StoreData provided from the randomizer 107 b. The randomizer 107 b outputsthe code data Store Data except for the parity data to the page buffer102, and the parity generation circuit 41 outputs the parity data to thepage buffer 102. Mixed data is written at the page buffer 102 as thecode data Store Data.

The ECC circuit 107 a and the randomizer 107 b are integrated on the ECCbus as illustrated in FIG. 24. Thus, randomizing and encoding aresimultaneously performed at ECC encoding, and decoding andde-randomizing are simultaneously performed at ECC decoding.

Returning to FIG. 24, page buffers 102 a to 102 d of the page buffer 102are configured to have the same circuit structure, which is describedwith reference to FIGS. 3 to 30. FIG. 26 is a diagram schematicallyillustrating a portion corresponding to a page buffer 102, a columncoding circuit 103, and an ECC column coding circuit 108 shown in FIG.24. FIGS. 27A and 27B are diagrams schematically illustrating a PB 4IOunit and a PB unit shown in FIG. 25. FIG. 28 is a circuit diagramschematically illustrating a PB unit. FIG. 29 is a circuit diagramschematically illustrating a PB unit according to another embodiment ofthe inventive concepts. FIG. 7 is a circuit diagram schematicallyillustrating a bit internal circuit 50 _(—) i (i being an integer of 0to 7) shown in FIGS. 28 and 29.

Referring to FIG. 25, a portion corresponding to a page buffer 102, acolumn coding circuit 103, and an ECC column coding circuit 108 shown inFIG. 24 has a PB4IO unit that latches four data from four IO lines andwrites data with respect to four IO lines.

In FIG. 26, there are shown ten PB4 IOs, that is, PB0 IO 0123 (PB 4IOunit) 30_0, PB0 IO 4567 (PB 4IO unit) 30_1, PB1 IO 0123 (PB 4IO unit)30_2, PB1 IO 4567 (PB 4IO unit) 30_3, PB2 IO 0123 (PB 4IO unit) 30_4,PB2 IO 4567 (PB 4IO unit) 30_5, PB3 IO 0123 (PB 4IO unit) 30_6, PB3 IO4567(PB 4IO unit) 30_7, PB4 IO 0123 (PB 4IO unit) 30_8, and PB4 IO 4567(PB 4IO unit) 30_9.

Here, an IO line is an input/output line installed between a multiplexer52 _(—) b and a PB control circuit 60 of a PB unit as will be more fullydescribed below. In exemplary embodiments, the IO line is electricallyconnected to any one of eight bit lines through a multiplexer 52 _(—) band eight bit circuits 51_0 a to 51_7 a. That is, the IO line is asignal line through which memory cell transistor data or data read froma memory cell transistor is transferred.

Since PB 4IO units shown in FIG. 26 have the same structure, a PB 4IOunit 30_0 shown in FIG. 26 is illustrated in FIG. 27A. The PB 4IO unit30_0 is formed of four PB units 30_00 to 30_03.

When an active level (e.g., a high level) of selection signal Sel_A<0>is provided from a column coding circuit 103, each of the PB units 30_00to 30_03 connects an IO line and a data bus (e.g., a second bus) (aswill be described below, a data bus Data_A<7:0>). In this case, asillustrated in FIG. 27A, four read data bits Data_Out_A<0> toData_Out_A<3> are read from four IO lines onto a data bus Data_A<3:0>.

Also, when an active level (e.g., a high level) of selection signalSel_B<0> is provided from an ECC column coding circuit 108, each of thePB units 30_00 to 30_03 connects an IO line and an ECC bus (e.g., afirst bus) (as will be described below, a data bus Data_B<19:0>). Inthis case, as illustrated in FIG. 27A, four read data bits Data_Out_B<0>to Data_Out_B<3> are read from four IO lines onto a data busData_B<3:0>.

Referring to FIG. 27B, PB units shown in FIG. 27A have the same circuitstructure. Each of PB units shown in FIG. 27A comprises eight bitcircuits 51_1 a to 51_7 a, a multiplexer 52 _(—) b, and a page buffer(PB) control circuit 60.

The multiplexer 52 _(—) b receives a column address signal Sub BL Codingfrom the column coding circuit 103 or the ECC column coding circuit 108shown in FIG. 24. The multiplexer 52 _(—) b selects one of the bitcircuits 51_1 a to 51_7 a based on the column address (e.g., a selectionsignal DIO<i> shown in FIG. 28). That is, the multiplexer 52 _(—) bconnects one of eight bit lines to the PB control circuit 60.

First, a detailed circuit of a PB unit will be more fully described withreference to FIGS. 28 and 30. FIG. 30 shows a circuit of each of bitinternal circuits 50_0 to 50_7 shown in FIG. 28. FIG. 30 shows a datasensing unit and a latch unit at a write operation and a driver unit fordriving a signal line at a read operation. In particular, each of thebit internal circuits 50_0 to 50_7 is implemented using transistors andinverter circuits. In addition, a combination of bit circuits 51_0 a to51_7 a and a multiplexer 52 _(—) b shown in FIG. 27B corresponds to thebit internal circuits 50_0 to 50_7. That is, since a bit internalcircuit is selected by a selection signal DIO, it partially has afunction of a bit circuit and a multiplexer 52 _(—) b.

As illustrated in FIG. 30, a bit internal circuit 50 _(—) i (i being aninteger of 0 to 7, eight bit internal circuits having the same circuitstructure) is formed of an inverter circuit 511, an inverter circuit512, a transistor 513, a transistor 514, a transistor 515, a transistor521, and a transistor 522. Here, the transistors 513, 514, 515, 521, and522 may be an N-channel MOS transistor.

A latch unit of the bit internal circuit 50 _(—) i is formed of theinverter circuits 511 and 512. Here, an input terminal of the inverter511 and an output terminal of the inverter 512 are connected to aconnection node N1, and an output terminal of the inverter 511 and aninput terminal of the inverter 512 are connected to a connection nodeN2. The connection node N1 is connected to a memory cell transistor (notshown) through a bit line. Data that a memory cell transistor storesappears on the connection node N1 as Data_i at a read operation. Datathat is to be stored in a memory cell transistor appears on theconnection node N1 as Data_i at a write operation. For example, when amemory cell transistor stores a low level (data 0), a voltage of Data_ihas a low level. When a memory cell transistor stores a high level (data1), a voltage of Data_i has a high level.

In the bit internal circuit 50 _(—) i, a driver unit is formed of thetransistors 515 and 522. The transistor 522 has a drain connected to aline of a read signal RD, a gate connected to a line of a selectionsignal DIO<i>, and a source connected to a drain of the transistor 515.The transistor 515 has a gate connected to the source of the transistor522, a gate connected to the connection node N2, and a source grounded.Here, the selection signal DIO<i> (i being 0˜7) is Sub BL Coding shownin FIG. 27B. For example, a column coding circuit 103 makes one ofselection signals DIO<7:0> become high based on a 3-bit address signalprovided from an address control circuit (not shown), or an ECC columndecoding circuit 108 makes one of the selection signals DIO<i> becomehigh based on a 3-bit address signal provided from an ECC circuit 107.By this, one of bit internal circuits 50_0 to 50_7 shown in FIG. 28 isselected.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data read operation on a memory cell transistor, alogical level of the read signal RD is equal to that of Data_i. That is,for example, when Data_i is at a high level with the read signal RDbeing pre-charged to a high level, the transistor 515 is turned off, thetransistor 522 is turned on, and the read signal RD retains a highlevel. When Data_i is at a low level, the transistor 515 is turned on,the transistor 522 is turned on, and the bit internal circuit 50 _(—) ichanges the read signal RD from a high level to a low level.

A line of the read signal RD is connected to a PB control circuit 60 asshown in FIG. 28. At a first mode of operation (e.g., an ECC mode), aline of the read signal RD is connected to ECC Bus in response to aselection signal Sel_B (a column address signal the ECC column codingcircuit 108 outputs). By this, Data_i of the bit internal circuit 50_(—) i is output on ECC Bus as a data read signal Data_Out_B.

Meanwhile, at a second mode of operation (e.g., a normal mode), a lineof the read signal RD is connected to Data Bus in response to aselection signal Sel_A (a column address signal a column coding circuit103 outputs). By this, Data_i of the bit internal circuit 50 _(—) i isoutput on Data Bus as a data read signal Data_Out_A.

Returning to FIG. 30, the transistors 513, 514, and 521 constitute asensing unit of the bit internal circuit 50 _(—) i. The transistor 513has a drain connected to the connection node N1, a gate connected to aline of a write signal DI, and a source connected to a drain of thetransistor 521. The transistor 514 has a drain connected to theconnection node N2, a gate connected to a line of a write signal nDI,and a source connected to the drain of the transistor 521. Thetransistor 521 has a drain connected to the source of the transistor 513and the source of the transistor 513, a gate connected to a line of aselection signal DIO<i>, and a source grounded.

The lines of the write signals DI and nDI are connected to the PBcontrol circuit 60 as shown in FIG. 28. As will be described below, as adata bus and ECCBus are connected by the selection signal Sel_B at thefirst mode of operation, a data write signal Data_In_B is received fromECCBus. By this, the PB control circuit 60 varies one of the writesignals DI and nDI from a low level to a high level in response to alevel of the data write signal Data_In_B. At this time, the other of thewrite signals DI and nDI retains a low level.

Meanwhile, at the second mode of operation, connection to Data Bus isperformed by the selection signal Sel_A, and a data write signalData_In_A is received from Data Bus. By this, the PB control circuit 60varies one of the write signals DI and nDI from a low level to a highlevel in response to a level of the data write signal Data_In_A. At thistime, the other of the write signals DI and nDI retains a low level.

With the above-described structure, if a selection signal DIO<i> goes toa high level at a data write operation on a memory cell transistor, aData_i level of the bit internal circuit 50 _(—) i is decided accordingto levels of the write signals DI and nDI. More particular, when one ofa data write signal Data_In_A and a data write signal Data_In_B is at alow level (data 0), the PB control circuit 60 outputs a high level ofwrite signal DI and a low level of write signal nDI. By this, thetransistor 513 is turned on and the transistor 514 is turned off. Atthis time, the connection node N1 is set to a low level and theconnection node N2 is set to a high level, so that Data_i has the samelogical low level (data 0) as that of a data bus.

When the data write signal Data_In_A or the data write signal Data_In_Bis at a high level (data 1), the PB control circuit 60 outputs a lowlevel of write signal DI and a high level of write signal nDI. By this,in the bit internal circuit 50 _(—) i, the transistor 513 is turned offand the transistor 514 is turned on. At this time, the connection nodeN1 is set to a high level and the connection node N2 is set to a lowlevel, so that Data_i has the same logical high level (data 1) as thatof a data bus.

Returning to FIG. 30, the PB control circuit 60 comprises a write unitperforming a data transfer from a data bus to a page buffer and a readunit performing a data transfer from a page buffer to a data bus. Theread unit of the PB control circuit 60 is formed of transistors 61 a and61 b. The transistors 61 a and 61 b may be an NMOS transistor. Thetransistor 61 a has a drain connected to a line of the read signal RD, agate connected to a line of the selection signal Sel_A, and a sourceconnected to Data Bus (e.g., a second data bus). The transistor 61 b hasa drain connected to a line of the read signal RD, a gate connected to aline of the selection signal Sel_B, and a source connected to ECC Bus(e.g., a first data bus).

Here, the selection signal Sel_A may be a column address signal that acolumn coding circuit 103 generates in response to address bits, forexample, an address Address A received from an address control circuit(not shown). The selection signal Sel_B may be a column address signalthat an ECC column coding circuit 108 generates in response to a part ofaddress bits, for example, an address Address B received from an ECCcircuit 107 shown in FIG. 24.

If a high level of selection signal Sel_B is received from the columnECC coding circuit 108 at a data read operation of an ECC mode (e.g., afirst mode of operation), the read unit of the PB control circuit 60turns on the transistor 61 b such that a line of the read signal RD isconnected to ECC Bus. By this, data of memory cell transistors (Data_iof a bit internal circuit) stored in the bit internal circuits 50_0 to50_7 are output to ECC Bus as a data read signal Data_Out_B.

If a high level of selection signal Sel_A is received from the columncoding circuit 103 at a data read operation of a normal mode (e.g., asecond mode of operation), the read unit of the PB control circuit 60turns on the transistor 61 a such that a line of the read signal RD isconnected to Data Bus. By this, data of memory cell transistors storedin the bit internal circuits 50_0 to 50_7 are output to Data Bus as adata read signal Data_Out_A.

The read unit of the PB control circuit 60 has the following structuresuch that when a memory cell transistor or a bit line connected to amemory cell transistor is abnormal in the page buffers 102 a and 102 c,data provided to the ECC circuit 107 has fixed data (e.g., fixed to data0) at a data read operation of an ECC mode. That is, the read unit ofthe PB control circuit 60 comprises a defect information storing unit 90a and a data fixing unit 90 b as illustrated in FIG. 28.

The defect information storing unit 90 a comprises inverter circuits 92and 93 and transistors 94, 95, and 96. Here, the transistors 94, 95, and96 may be an N-channel MOS transistor. A latch unit of the defectinformation storing unit 90 a is formed of the inverter circuits 92 and93. The inverter circuit 92 has an output terminal connected to aconnection node N4 and an input terminal of the inverter 93 and an inputterminal connected to a connection node N3 and an output terminal of theinverter circuit 94. The connection node N3 is connected to a firstinput terminal of the AND circuit 91. The connection node N3 provides adefect signal PB_Defect indicating that data stored in the latch unit isdefective. The connection node N4 provides a defect signal nPB_Defectindicating that data stored in the latch unit is defective.

A sensing unit of the defect information storing unit 90 a comprisestransistors 94, 95, and 96. The transistor 94 has a drain connected tothe connection node N3, a gate connected to a line of a defectinformation signal SDI, and a source connected to a drain of thetransistor 96. The transistor 95 has a drain connected to the connectionnode N4, a gate connected to a line of a defect information signal nSDI,and a source connected to the drain of the transistor 96. The transistor96 has a drain connected to the source of the transistor 94 and thesource of the transistor 95, a gate connected to a line of a power-onreset signal POR_Mode, and a source grounded.

Here, the defect information signal SDI and the defect informationsignal nSDI are signals indicating whether a bit line connected to thePB control circuit 60 or a memory cell transistor connected to acorresponding bit line is defective. In the event that a test resultexecuted after fabrication indicates that a bit line connected to the PBcontrol circuit 60 is defective, the defect information signal SDI isset to data 0 (e.g., a low level) and the defect information signal nSDIis set to data 1 (e.g., a high level). Or, in the event that a testresult executed after fabrication indicates that a bit line connected tothe PB control circuit 60 is defective, the defect information signalSDI is set to a high level and the defect information signal nSDI is setto a low level. Before shipment, such defect information signals arestored at a storage area for system, for example, of the NAND flashmemory 10 in connection with the selection signal Sel_B indicating alocation of the PB control circuit 60. Also, the power-on reset signalPOR_Mode is a signal maintaining a high level during a predeterminedtime period (e.g., a time period where the defect information signalsare transferred to the PB control circuit 60 from the storage area forsystem) after the NAND flash memory 10 is powered up.

When the NAND flash memory 10 is powered up, the power-on reset signalPOR_Mode goes to a high level. If a bit line connected to the PB controlcircuit 60 is defective, the defect information storing unit 90 a turnsoff the transistor 94 and turns on the transistor 95. By this, the nodeN3 is set to a high level and the node N4 is set to a low level. In thiscase, the defect signal PB_Defect has a high level. Since the power-onreset signal POR_Mode goes to a low level after a transfer period, thedefect information storing unit 90 a maintains the defect signalPB_Defect at a high level during a period where a power is supplied tothe NAND flash memory 10.

When the NAND flash memory 10 is powered up, the power-on reset signalPOR_Mode goes to a high level. If a bit line connected to the PB controlcircuit 60 is not defective, the defect information storing unit 90 aturns on the transistor 94 and turns off the transistor 95. By this, thenode N3 is set to a low level and the node N4 is set to a high level. Inthis case, the defect signal PB_Defect has a low level. Since thepower-on reset signal POR_Mode goes to a low level after a transferperiod, the defect information storing unit 90 a maintains the defectsignal PB_Defect at a low level during a period where a power issupplied to the NAND flash memory 10.

The data fixing unit 90 b is formed of the AND circuit 91 and atransistor 61 c. Here, the transistor 61 c is an NMOS transistor. TheAND circuit 91 is a 2-input 1-output logic circuit. The AND circuit 91has a first input terminal connected to the connection node N3 and asecond input terminal connected to a line of the selection signal Sel_A,and an output terminal connected to a gate of the transistor 61 c. Thetransistor 61 c has a drain connected to a line of a read signal RD, agate connected to the output terminal of the AND circuit 91, and asource grounded.

In the event that a bit line connected to the PB control circuit 60 isnot defective, the defect signal PB_Defect has a low level. In thiscase, since the AND gate 91 outputs a low level of output signal, thetransistor 61 c of the data fixing unit 90 b is turned off. That is, thedata fixing unit 90 b does not operate. Meanwhile, in the event that abit line connected to the PB control circuit 60 is defective, the defectsignal PB_Defect has a high level. When ECC is used, that is, at an ECCmode, if a high level of selection signal Sel_B is provided to the ANDcircuit 91, the AND circuit 91 outputs a high level of output signal, sothat the transistor 61 c is turned on. In this case, ECCBus_(—)1 isgrounded such that Data_Out_B is fixed to a low level (e.g., a GNDlevel). That is, in the event that a bit line connected to the PBcontrol circuit 60 is defective, at the ECC mode, the PB control circuit60 acts as a data fixing circuit that outputs read data Data_Out_Bhaving a fixed level (e.g., a low level) to ECCBus_(—)1.

In addition, at a data read operation of a normal mode, since the PBcontrol circuit 60 is selected by the selection signal Sel_A, the ANDcircuit 91 outputs a low-level signal. In this case, the data fixingunit 90 b being an additional circuit does not operate. If the defectsignal PB_Defect is directly provided to a gate of the transistor 91 cwithout using the AND circuit 91, the read signal RD is fixed to a lowlevel when a bit line connected to the PB control circuit 60 isdefective. That is, the PB control circuit 60 acts as a data fixingcircuit that outputs a fixed level (e.g., a low level) of read dataData_Out_A on DataBus_(—)1 when the selection signal Sel_A is receivedat a normal mode and outputs a low level of read data Data_Out_B whenthe selection signal Sel_B is received at an ECC mode.

The defect information storing unit 90 a and the data fixing unit 90 bshown in FIG. 28 may be configured as illustrated in FIG. 29. FIG. 29shows another circuit structure of a PB unit. In FIG. 29, constituentelements that are the same as those in FIG. 28 are marked by the samereference numerals, and a description thereof is thus omitted. Thedefect information storing unit 90 a shown in FIG. 29 is configured thesame as that shown in FIG. 28. But, the data fixing unit 90 b shown inFIG. 28 is replaced with a data fixing unit 90 b′. A signal on aconnection node N4 of the defect information storing unit 90 a is usedas a defect signal nPB_Defect. The data fixing unit 90 b′ is formed of atransistor 61 c. The transistor 61 c has a source connected to ECCBus(e.g., a first data bus). The transistor 61 b has a drain connected to aline of the read signal RD, a gate connected to a line of the selectionsignal Sel_B, and a source connected to a drain of the transistor 61 c.

In the event that a bit line connected to the PB control circuit 60 isdefective, the defect signal nPB_Defect has a low level. In this case,since the transistor 61 c is turned off, a transfer path between theread signal RD and ECCBus_(—)1 is blocked. For this reason, read dataData_Out_B is fixed to a high level through a pull-up circuit.Meanwhile, in the event that a bit line connected to the PB controlcircuit 60 is not defective, the defect signal nPB_Defect has a lowlevel. In this case, since the transistor 61 c is turned on. By this,the read signal RD, that is, data of a memory cell transistor is outputonto ECCBus_(—)1 such that it is read as read data Data_Out_B.

As compared with a data fixing unit 90 b shown in FIG. 29, the datafixing unit 90 b′ has such a merit that an AND circuit is not requiredsince the transistors 61 b and 61 c are connected in series between aline of the read signal RD and ECCBus_(—)1.

In the data fixing unit 90 b′ shown in FIG. 29, if the transistor 61 cis inserted between a line of the read signal RD and the transistor 61 aand a drain of the transistor 61 b, that is, between a line of the readsignal RD and the PB control circuit 60, the PB control circuit 60 actsas a data fixing circuit that outputs a fixed level (e.g., a high level)of read data Data_Out_A to DataBus_(—)1 in response to the selectionsignal Sel_A provided at the normal mode and a high level of read dataData_Out_B in response to the selection signal Sel_B provided at the ECCmode. As described above, in the event that a bit line connected to thePB control circuit 60 is defective, data Data_Out_A or Data_Out_B mayhave a low level or a high level of fixed value.

Returning to FIG. 28, the write unit of the PB control circuit 60comprises inverter circuits 62, 63, 67, NAND circuits 64 and 65, an ORcircuit 66, and switches 68 and 69. The inverter circuit 62 is a logicalinversion circuit, and has an output terminal connected to a line of thewrite signal DI and an input terminal connected to an output terminal ofthe NAND circuit 64. The inverter circuit 63 is a logical inversioncircuit, and has an output terminal connected to a line of the writesignal nDI and an input terminal connected to an output terminal of theNAND circuit 65.

The NAND circuit 64 is a 3-input 1-output NAND circuit, and has a firstinput terminal connected to a line of a write enable signal fDinEnable,a second input terminal connected to an output terminal of the ORcircuit 66, and a third input terminal connected to an output terminalof the inverter circuit 67. An output terminal of the NAND circuit 64 isconnected to an input terminal of the inverter circuit 62. The NANDcircuit 65 is a 3-input 1-output NAND circuit, and has a first inputterminal connected to a line of the write enable signal fDinEnable, asecond input terminal connected to the output terminal of the OR circuit66, and a third input terminal connected to a first input/outputterminal of the switch 68 and a first input/output terminal of theswitch 69. An output terminal of the NAND circuit 65 is connected to aninput terminal of the inverter circuit 63.

The OR circuit 66 is a 2-input 1-output logic circuit, and has a firstinput terminal connected to an output of an AND circuit 71 and a secondinput terminal connected to a line of the selection signal Sel_A. Anoutput terminal of the OR circuit 66 is connected to the second inputterminal of the NAND circuit 64 and the second input terminal of theNAND circuit 65. The AND circuit 71 logically combines the selectionsignal Sel_B and the defect signal nPB_Defect. By this, in a case wherethe defect signal nPB_Defect has a high level (not defective), theselection signal Sel_B has a high level. At this time, the second inputterminal of the NAND circuit 65 has a high level, so that a writecondition is satisfied. Meanwhile, in a case where the defect signalnPB_Defect has a low level (e.g., a defective page buffer), at a mode ofoperation of the selection signal Sel_B, the second input terminal ofthe NAND circuit 65 does not have a high level. Thus, a write conditionis not satisfied. The inverter circuit 67 is a logical inversioncircuit, and has an input terminal connected to the first input/outputterminal of the switch 68 and the first input/output terminal of theswitch 69 and an output terminal connected to the third input terminalof the NAND gate 64.

The switch 68 is a bidirectional switch, and has the first input/outputterminal connected to the input terminal of the inverter circuit 67 andthe third input terminal of the NAND circuit 65 and a secondinput/output terminal connected to Data Bus. The switch 69 is abidirectional switch, and has the first input/output terminal connectedto the input terminal of the inverter circuit 67 and the third inputterminal of the NAND circuit 65 and a second input/output terminalconnected to ECC Bus. In addition, an input of the inverter circuit 67is pulled up by a PMOS transistor such that an input of the invertercircuit 67 is not set to a “don't care” state when any one of thebidirectional switches is unselected.

With the above-described structure, when at a data write operation ofthe ECC mode (e.g., a first mode of operation), the write enable signalfDinEnable is at a high level and the selection signal Sel_B is at ahigh level, the write unit of the PB control circuit 60 turns on theswitch 69 such that one of the write signals DI and nDI transitions froma low level to a high level in response to a level of the data writesignal Data_In_B received from ECC Bus. More particular, when the datawrite signal Data_In_B is at a low level (data 0), the write signal DItransitions to a high level. By this, Data_i of one of the bit internalcircuits 50_0 to 50_7 goes to a low level. Afterwards, data 0 is writtenat a memory cell transistor through a program operation. Meanwhile, whenthe data write signal Data_In_B is at a high level (data 1), the writesignal nDI transitions to a high level. By this, Data_i of one of thebit internal circuits 50_0 to 50_7 goes to a high level. Afterwards,data 1 is written at a memory cell transistor through a programoperation.

If the write enable signal fDinEnable and the selection signal Sel_A goto a high level at a data write operation of a normal mode (e.g., asecond mode of operation), the write unit of the PB control circuit 60turns on the switch 68 such that one of the write signals DI and nDItransitions from a low level to a high level in response to a level ofthe data write signal Data_In_A received from DataBus. More particular,when the data write signal Data_In_A is at a low level (data 0), thewrite signal DI transitions to a high level. By this, Data_i of one ofthe bit internal circuits 50_0 to 50_7 goes to a low level. Afterwards,data 0 is written at a memory cell transistor through a programoperation.

Meanwhile, when the data write signal Data_In_A is at a high level (data1), the write signal nDI transitions to a high level. By this, Data_i ofone of the bit internal circuits 50_0 to 50_7 goes to a high level.Afterwards, data 1 is written at a memory cell transistor through aprogram operation.

As described above, the PB control circuit 60 is a circuit that controlsa data transfer between a data bus (a first data bus and a second databus) and a memory cell transistor connected through a bit line to one,selected by the selection signal DIO<i>, from among the bit internalcircuits 50_0 to 50_7 constituting a PB unit of a page buffer 102.

The line of the read signal RD, the line of the write signal DI, and theline (IO line) of the write signal nDI are lines connecting the PBcontrol circuit 60 and the bit internal circuits 50_0 to 50_7constituting the PB unit, and are input/output lines for a data transferof the PB unit. Thus, the PB control circuit 60 transfers write data andread data between an input/output unit of the page buffer 102 and thefirst and second data buses ECC Bus and Data Bus.

Returning to FIG. 27A, by the above-described PB control circuit 60, aPB 4IO unit 30_0 operates as follows. When a high level of selectionsignal Sel_A<0> is received from the column coding circuit 103, the PB4IO unit 30_0 connects input/output lines IO_0 to IO_3 (in FIG. 28,marked by RD) of four page buffers to a 4-bit data bus Data_A<3:0>. Bythis, the PB 4IO unit 30_0 outputs the data read signals Data_Out_A<3>to Data_Out_A<0> (hereinafter, referred to as data read signalsData_Out_A<3:0>) on the data bus Data_A<3:0>.

When a high level of selection signal Sel_B<0> is received from the ECCcolumn coding circuit 108, the PB 4IO unit 30_0 connects input/outputlines IO_0 to IO_3 of four page buffers to a 4-bit ECC bus Data_B<3:0>(here, referred to as data bus Data_B<3:0>). By this, the PB 4IO unit30_0 outputs the data read signals Data_Out_B<3> to Data_Out_B<0>(hereinafter, referred to as data read signals Data_Out_B<3:0>) on thedata bus Data_B<3:0>.

Returning to FIG. 26, by the above-described PB 4IO unit 30_0, a pagebuffer 102, a column coding circuit 103 and an ECC column coding circuit108 (here, referred to as a data read model) operate as follows at adata read operation. Also, input/output lines (e.g., data read lines RDshown in FIGS. 28 and 29) of page buffers connected to PB 4IO units 30_1to 30_9 shown in FIG. 26 are referred to as IO lines IO_4 to IO_7, IOlines IO_8 to IO_11, IO lines IO_12 to IO_15, IO lines IO_16 to IO_19,IO lines IO_20 to IO_23, IO lines IO_24 to IO_27, IO lines IO_28 toIO_31, IO lines IO_32 to IO_35, and IO lines IO_36 to IO_39. Also, DataBus has an 8-bit bus width, and is referred to as a data busData_A<7:0>. ECC Bus has a 20-bit bus width, and is referred to as adata bus Data_B<19:0>.

At the normal mode (e.g., the second mode of operation), the columncoding circuit 103 sets one of column addresses of selection signalsSel_A<0> to Sel_A<4> to a high level and the remaining thereof to a lowlevel and then the selection signals Sel_A<0> to Sel_A<4> to the dataread model. For example, at the normal mode, 40-bit data of the IO linesIO_0 to IO_39 is sequentially output onto the data bus Data_A<7:0> bysequentially providing the selection signals Sel_A<0> to Sel_A<4> to thedata read model.

When the selection Sel_A<0> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0 and the PB 4IO unit 30_1 connect the IO lines IO_0 to IO_7 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_0 and the PB 4IO unit30_1 output read data Data_Out_A<7:0> (data on the IO lines IO_0 toIO_7) on the data bus Data_A<7:0>.

When the selection Sel_A<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_2 and the PB 4IO unit 30_3 connect the IO lines IO_8 to IO_15 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_2 and the PB 4IO unit30_3 output read data Data_Out_A<7:0> (data on the IO lines IO_8 toIO_15) on the data bus Data_A<7:0>.

When the selection Sel_A<2> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_4 and the PB 4IO unit 30_5 connect the IO lines IO_16 to IO_23 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_4 and the PB 4IO unit30_5 output read data Data_Out_A<7:0> (data on the IO lines IO_16 toIO_23) on the data bus Data_A<7:0>.

When the selection Sel_A<3> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_6 and the PB 4IO unit 30_7 connect the IO lines IO_24 to IO_31 to thedata bus Data_A<7:0>. By this, the PB 4IO unit 30_6 and the PB 4IO unit30_7 output read data Data_Out_A<7:0> (data on the IO lines IO_24 toIO_31) on the data bus Data_A<7:0>.

Finally, when the selection Sel_A<4> goes to a high level, thetransistor 61 a of the PB control circuit 60 is turned on. At this time,the PB 4IO unit 30_8 and the PB 4IO unit 30_9 connect the IO lines IO_32to IO_39 to the data bus Data_A<7:0>. By this, the PB 4IO unit 30_8 andthe PB 4IO unit 30_9 output read data Data_Out_A<7:0> (data on the IOlines IO_32 to IO_39) on the data bus Data_A<7:0>.

As described above, if the selection signal Sel_A is provided to thedata read model five times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_A<7:0> by the 8-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on Data Busthrough bit lines and IO lines IO_0 to IO_39.

At the ECC mode (e.g., the first mode of operation), the ECC circuit 107sets one of column addresses of the selection signals Sel_B<0> andSel_B<1> to a high level and the other to a low level and outputs themto the data read model. 40-bit data of the IO lines IO_0 to IO_39 issequentially read on a data bus Data_B<19:0> by sequentially providingthe selection signals Sel_B<0> and Sel_B<1> to the data read mode.

When the selection Sel_B<0> goes to a high level, the transistor 61 b ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_0, 30_2, 30_4, 30_6, and 30_8 connect the data bus Data_B<19:0> to IOlines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, andIO_32 to IO_35. By this, the PB 4IO unit 30_0, 30_2, 30_4, 30_6, and30_8 output read data Data_Out_B<19:0> (data on the IO lines IO_0 toIO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32 to IO_35)on the data bus Data_B<19:0>.

When the selection Sel_B<1> goes to a high level, the transistor 61 a ofthe PB control circuit 60 is turned on. At this time, the PB 4IO unit30_1, 30_3, 30_5, 30_7, and 30_9 connect the data bus Data_B<19:0> to IOlines IO_4 to IO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, andIO_36 to IO_39. By this, the PB 4IO unit 30_1, 30_3, 30_5, 30_7, and30_9 output read data Data_Out_B<19:0> (data on the IO lines IO_4 toIO_7, IO_12 to IO_15, IO_20 to IO_23, IO_28 to IO_31, and IO_36 toIO_39) on the data bus Data_B<19:0>.

As described above, if the selection signal Sel_B is provided to thedata read model two times, the PB 4IO units 30_0 to 30_9 connect the IOlines IO_0 to IO_39 to the data bus Data_B<19:0> by the 20-IO unit. Bythis, 40-bit data stored in memory cell transistors are read on ECC Busthrough bit lines and IO lines IO_0 to IO_39. For example, when aselection signal is not provided five times at the normal mode, data onIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not read on Data Bus. If a selection signal (e.g.,Sel_B<0>) is provided once at the ECC mode, data of the IO lines IO_0 toIO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27, and IO_32 to IO_35may be read out on ECC Bus.

FIG. 31 is a diagram for describing a data write operation of a portioncorresponding to a page buffer 102, a column coding circuit 103 and anECC column coding circuit 108 shown in FIG. 24. A data write operationof a page buffer 102, a column coding circuit 103 and an ECC columncoding circuit 108 (here, referred to as a data write model) isperformed by an operation of a PB 4IO unit 30_0. A data transfer of thedata write model is performed in a direction opposite to a directionshown in FIG. 132, and a description thereof is thus omitted.

In the data write model, for example, at a normal mode, data provided toIO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19, IO_24 to IO_27,and IO_32 to IO_35 is not written from Data Bus when a selection signalis not provided five times. In this behalf, if a selection signal (e.g.,Sel_B<0>) is provided once at the ECC mode, the remaining data iswritten on the IO lines IO_0 to IO_3, IO_8 to IO_11, IO_16 to IO_19,IO_24 to IO_27, and IO_32 to IO_35 from ECC Bus.

A semiconductor memory device (or, a semiconductor memory device) 10 ofthe inventive concepts comprises a first data bus Data_B<19:0>, a seconddata bus Data_A<7:0> being different in number from the first data busand independent from the first data bus Data_B<19:0>, and a datatransfer unit (e.g., a PB control circuit 60 of each of PB 4IO units30_0 to 30_9). When a data transfer with memory cells is performed atthe first mode of operation, the data transfer unit connects bit lines,being equal in number to the first data bus, from among a plurality ofbit lines to the first data bus to transfer data. When a data transferwith memory cells is performed at the second mode of operation, the datatransfer unit connects bit lines, being equal in number to the seconddata bus, from among a plurality of bit lines to the second data bus totransfer data.

If the number of bit lines is n (n being a common multiple of p and qbeing a natural number, p>q), the first data bus is q, and the seconddata bus is q. If (n/p) address signals are received at the first modeof operation, the data transfer unit connects p bit lines to the p firstdata bus. If (n/q) address signals are received at the second mode ofoperation, the data transfer unit connects q bit lines to the seconddata bus.

Also, the NAND flash memory 10 comprises a memory array 101, a pagebuffer 82 configured to read data from the memory array 101 by the pageunit and to store read data read from the memory array 101, an ECCcircuit 107 configured to correct an error on the read data transferredfrom the page buffer 82 and to write the error-corrected data back inthe page buffer 82, and an IO pad (or, an interface unit) 106 configuredto output the read data written back in the page buffer 82. ECC Bus isconnected to the ECC circuit 107, and Data Bus is connected to the IOpad 106.

In the NAND flash memory 10, the page buffer 82 stores write datareceived through the IO pad 106, and the ECC circuit 107 generatesparity data on the write data transferred from the page buffer 82. Theparity data and write data are written back in the page buffer.

By this, it is possible to control column coding, that is, addressesindependently by preparing a plurality of data buses (e.g., ECC Bus andData Bus). In exemplary embodiments, it is possible to control addressesindependently by forming a data bus to be independent from input/outputlines of the page buffer 102 (e.g., IO_0 to IO_39), that is, a portiondirectly connected to the page buffer. Thus, the semiconductor memorydevice according to an embodiment of the inventive concepts obtains thefollowing effects.

(1) A high-speed operation is implemented by widening a bus width at thefirst mode of operation (e.g., the ECC mode). There is described such acase that when a column address is received once, 8-bit data istransferred to Data Bus at the second mode of operation (e.g., thenormal mode) and 20-bit data is transferred at the ECC mode. A bus widthis easily widened according to an input of Address_B, that is, columncoding to the page buffer 102. For example, if two column addresses areused for 1024 PB units, it is possible to transfer data with the ECC Busbeing widened a 512-bit bus width at the ECC mode. Also, it is possibleto form a data bus independent from a portion directly connected to thepage buffer and to control addresses independently. For this reason, ascompared with the case that data is transferred to an ECC circuit usinga part of the data bus like a conventional technique, a high-speed datatransfer is implemented. The reason is that there is not required acircuit (e.g., a first latch circuit 70 of a conventional example)associated with address control for separating a data transfer at thenormal mode and a data transfer at the ECC mode. In particular, in caseof a defective PB unit, since the PB control circuit 60 transfers fixeddata to the ECC circuit 107 through ECC Bus, it is unnecessary totransfer data repaired through the column repair circuit 104 on ECCprocessing to the ECC circuit 107 through ECC Bus. Also, it isunnecessary to dispose the column repair circuit 104 on ECC Bus the buswidth of which is widened. For this reason, a time taken to transferdata from a page buffer to an ECC circuit at ECC processing is shortenedby a time taken for repair processing of the column repair circuit 104.Also, since it is unnecessary to widen a bus width of Data Bus (e.g., asecond data bus) at ECC processing, an increase in a circuit size of thecolumn repair circuit 104 is suppressed.

(2) Freedom on address control and mapping is improved. At a normalmode, when 8-bit data is transferred using a column address, forexample, data of IO lines IO_0 to IO_7 is transferred to Data Bus byproviding a selection signal Sel_A<0> to PB 4IO units 30_0 and 30_1. Inthis behalf, at an ECC mode, data on all addresses is transferred to theECC circuit in a lump by allocating an address independent from theselection signals Sel_B<0> and Sel_B<1> to the PB 4IO units 30_0 and30_1. For example, although normal data and parity data are assigned todifferent addresses of the selection signal Sel_A at a normal mode, theyare assigned to the same address of the selection signal Sel_B at theECC mode, and normal data and parity data are transferred to the ECCcircuit in a lump. Thus, address control at the second mode of operationand address control at the first mode of operation are independent fromeach other, and freedom of address mapping is high.

Also, at the normal mode, a column address is used with respect to fiveselection signals Sel_A<0> to Sel_A<4>. At the ECC mode, a columnaddress is used with respect to two selection signals Sel_B<0> andSel_B<1>. This means that although a column address has a value notbeing 2^(n) in case of the user specification of the normal mode, it iseasy to change an address space of the ECC mode to a unit space having avalue of 2^(n). By this, a code composition of the ECC circuit 107, forexample, a code length (e.g., optimization on code length composition incase of cumulative coding) may be decided with freedom, and optimalperformance is achieved.

(3) A design change is easily made. In case of designing a productincluding an ECC circuit, it is assumed that a product is a derivationproduct and a product not including an ECC circuit is separatelydesigned. In this case, data buses and column coding circuits associatedwith address control are independent with respect to the ECC mode andthe normal mode. By this, it is possible to separate a circuitassociated with the ECC mode and a circuit associated with the normalmode. Thus, it is easy to eliminate the circuit associated with the ECCmode. This means that a design change is easily made.

An example where a NAND flash memory shown in FIG. 24 operates at thefirst mode of operation and the second mode of operation is describedwith reference to a page buffer 102 and an operation flow chart. FIG.32A through 32C are diagrams for describing each page buffer of a pagebuffer 102. FIGS. 33A through 33D are flow charts for describing anoperation of a page buffer 102. In FIG. 32A, there are schematicallyillustrated a page buffer 120 a for main data (normal data), a pagebuffer 102 b for column repair for main data (repair data of normaldata), a page buffer 102 c for ECC parity (parity data), and a pagebuffer 102 d for parity's column repair (repair data of parity data). InFIG. 32A, numbers indicate PB units (e.g., a PB control circuit 60 andbit internal circuits 50_0 to 50_7 shown in FIGS. 28 and 29)constituting the page buffers 102 a to 102 d. The numbers are numbers ofselection signals Sel_A indicating locations of PB units, that is,Coding shown in FIG. 27B. That is, the page buffer 102 a includes 256 PBunits 0 to 255 for normal data, the page buffer 102 b includes 8 PBunits 256 to 263 for repair of normal data, the page buffer 102 cincludes 36 PB units 264 to 299 for parity data, and the page buffer 102d includes 8 PB units 300 to 307 for repair of parity data.

In FIG. 32B, there is illustrated an example in which when eight bitlines connected to a PB unit 1 of the page buffer 102 a or memory celltransistors connected to eight bit lines are defective, the PB unit 1 ofthe page buffer 102 a is replaced with a PB unit 256 of the page buffer102 b. Also, in FIG. 32B, there is illustrated an example in which wheneight bit lines connected to a PB unit 265 of the page buffer 102 c ormemory cell transistors connected to eight bit lines are defective, thePB unit 265 of the page buffer 102 c is replaced with a PB unit 300 ofthe page buffer 102 d. PB units 257 to 263 of the page buffer 102 bcorresponding to a slashed portion in FIG. 32B are unused PB units, sothat the PB units 257 to 263 are not selected by a column coding circuit103 under a control of a column repair circuit 104. That is, the PBunits 257 to 263 may be at an inactive state. PB units 301 to 307 of thepage buffer 102 d corresponding to a slashed portion in FIG. 32B areunused PB units, so that the PB units 301 to 307 are not selected by anECC column coding circuit 108 under a control of a parity column repaircircuit 105. That is, the PB units 301 to 307 may be at an inactivestate.

At a normal mode, since the PB unit 1 of the page buffer 102 a is notselected and the PB unit 256 replaced is selected by a selection signalSel_A, read data Data_Out_A (e.g., data read from the PB unit 1) isoutput to an I/O pad 106 through DataBus_(—)1, DataBus_(—)2, andDataBus_(—)3 (e.g., a second data bus). If write data is received fromthe I/O pad 106 at the normal mode, it is provided to the PB unit 255through DataBus_(—)3, DataBus_(—)2, and DataBus_(—)1 as the write dataData_A_In (data to be stored in the PB unit 1). As described above, aregion of a page buffer where a user may provide a column address isfrom the PB unit 0 to the PB unit 255. That is, the PB unit 256 to 263of the page buffer 102 b, the PB units 264 to 299 of the page buffer 102c, and the PB units 300 to 307 of the page buffer 102 d form a pagebuffer region that is inaccessible by a user.

The PB unit 1 of the page buffer 102 a is selected by a selection signalSel_B at an ECC mode, and read data Data_Out_B fixed to a low level or ahigh level is transferred to an ECC circuit 107 through ECCBus_(—)1 andECCBus_(—)2 (e.g., a first data bus) to be used for ECC processing.Also, the repaired PB unit 256 is selected by the selection signalSel_B, and read data Data_Out_B is transferred to the ECC circuit 107through ECCBus_(—)1, ECCBus_(—)2, and ECCBus_(—)3 to be used for ECCprocessing as read data of the PB unit 1 seen from the user. At the ECCmode, if the ECC processing is ended, data to be written back at the PBunit 1 is provided to the PB unit 255 through ECCBus_(—)3, ECCBus_(—)2,and ECCBus_(—)1 (e.g., a first data bus) as write data Data_A_In. Inaddition, data, corresponding to PB units 0 to 255, from amongECC-processed data may be provided to the external device as clear datathrough a data bus Data_A.

The PB unit 265 of the page buffer 102 c is selected by the selectionsignal Sel_B at the ECC mode, and read data Data_Out_B fixed to a lowlevel or a high level is transferred to a parity column repair circuit105 through ECCBus_(—)1 and ECCBus_(—)2 (e.g., data bus Data_B). Also,the repaired PB unit 300 is selected by the selection signal Sel_B, andread data Data_Out_B is transferred to the parity column repair circuit105 through ECCBus_(—)1 and ECCBus_(—)2 to repair processing. At the ECCmode, if the ECC processing is ended, data to be written back at the PBunit 265 is provided to the parity column repair circuit 105 throughECCBus_(—)3 for repair processing, and resultant data is then providedto the PB unit 300 through ECCBus_(—)2 and ECCBus_(—)1 (e.g., a firstdata bus) as write data Data_B_In. In addition, ECC-processed data isnot output to the external device through the data bus Data_A asdescribed above.

A data write operation to a memory cell transistor and a data readoperation from a memory cell transistor are described with reference toFIG. 33A through 33D. FIG. 33A shows a data write operation, FIG. 33Bshows a data read operation, FIG. 33C show a randomizing and encodingoperation of a randomizer and ECC circuit 107 shown in FIG. 25, and FIG.33D shows a de-randomizing and decoding operation of a randomizer andECC circuit 107 shown in FIG. 25. An operation of the page buffer 102 atan ECC mode is in detail described mainly based on a repair operation.

Data Write Operation

In step ST1, a user provides a NAND flash memory 10 with a predeterminedcommand (e.g., a write command), an address (here, indicating a columnaddress selecting a PB unit 1), and write data through an I/O pad 106.In step ST2, a repair of normal data is executed. More particular, acolumn coding circuit 103 selects a PB unit 256 instead of a PB unit 1under a control of a column repair circuit 104 such that the write datais stored in the PB unit 256.

After a time elapses, the method proceeds step ST6 when a mode is anormal mode (e.g., a second operation mode) where the user invokes aprogram execution command. In step ST6, programming is executed suchthat data is transferred to a memory cell transistor from a page bufferthrough a bit line. In case of an ECC mode (e.g., a first mode ofoperation), the method proceeds to step ST5 to execute an ECC encodingoperation as follows.

Here, FIG. 32C shows a code structure at ECC processing. A data unit isdata stored in PB units 0 to 263, and a parity unit (ECC unit) is datastored in PB units 264 to 299. Data to be written in the PB unit 1 isstored in the PB unit 256, and data stored in memory cell transistorsare read and stored in PB units 0 and 2 to 255 through connectedthereto. In step ST31, data stored in the PB units 0 to 263 is providedto a randomizer and ECC circuit 107 through ECCBus_(—)1, ECCBus_(—)2,and ECCBus_(—)3 (e.g., a first data bus).

As described above, at this time, fixed data (e.g., L data in case of aPB control circuit 60 shown in FIG. 28 or H data in case of a PB controlcircuit 60 shown in FIG. 29) is provided from the PB unit 1 to therandomizer and ECC circuit 107. Data that is data to be written in thePB unit but data written in the PB unit 256 is provided to the ECCcircuit 107 from the PB unit 256. A randomizer 107 b performs a datarandomizing operation (ST32 a) and outputs randomized data to an ECCcircuit 107 a. The ECC circuit 107 a generates parity data by encodingthe randomized data (ST32 b).

The randomizer and ECC circuit 107 writes ECC-processed data back in thePB units 0 to 307 (ST33). Here, data of the randomizer 107 b (refer toFIG. 25) is written back in PB units 0 to 263, and data of a paritygeneration circuit 41 is written back in PB units 264 to 307. At thistime, an ECC coding circuit 108 selects a PB unit 300 instead of a PBunit 265 under a control of a column repair circuit 105. By this, paritydata to be written back in the PB unit 265 is stored in the PB unit 300.Data randomized data in step S32 a is written at the PB units 0 to 263,and parity data is written at the PB units 264 and 307 (refer to aslashed portion in FIG. 32B). Data is not written at an inactive pagebuffer by a circuit shown in FIG. 28 or 29.

Since data Data_i to be written at a memory cell is latched by a latchunit (refer to FIG. 30) of each PB unit, a memory cell transistor isprogrammed (ST6). Data is iteratively provided to a memory cell from alatch unit of each PB unit until a program operation is passed (ST7). Ifthe program operation is passed, the iterative process is ended(ST7—Yes). If the program operation is not passed, the procedure goes tostep ST6 for a program operation until the program operation is passed(ST7—No).

Data Read Operation

A user provides a predetermined command (e.g., a read command) and anaddress (e.g., a column address selecting the PB unit 1) (ST11). Data ofa memory cell transistor is sensed by a latch unit of each PB unit andthe sensed data is latched on a connection node N1 of a bit internalcircuit show in FIG. 29 (ST12). Data_i is latched by the latch unit ofthe bit internal circuit (ST13). In case of a normal mode (e.g., asecond mode of operation), the procedure goes to step ST15 to end asensing operation. In case of an ECC mode (e.g., a first mode ofoperation), the procedure goes to step ST14 to perform an ECC decodingoperation as follows.

Data stored in PB units 0 to 299 is provided to the randomizer and ECCcircuit 107 through ECC Bus_(—)1, ECC Bus_(—)2, and ECC Bus_(—)3 (afirst data bus) (ST41). As described above, at this time, fixed data(e.g., L data in cased of a PB control circuit 60 shown in FIG. 28 or Hdata in case of a PB control circuit 60 shown in FIG. 29) is provided toa syndrome calculation circuit 31 of the ECC circuit 107 a (refer toFIG. 25) from the PB unit 1. Also, data that is data to be written atthe PB unit 1 but data to be written at the PB unit 256 is provided tothe syndrome calculation circuit 31 of the ECC circuit 107 a from the PBunit 256. Also, parity data that is data to be written at the PB unit300 but data to be written at the PB unit 265 is provided to the paritycolumn repair circuit 105 from the PB unit 265 through ECC Bus_(—)1 andECC Bus_(—)2 for repairing, and resultant data is provided to thesyndrome calculation circuit 31 of the ECC circuit 107 a through ECCBus_(—)3. The randomizer and ECC circuit 107 corrects an error of datastored in PB units 0 to 263 by performing a decoding operation based onparity data (ST42 a). The randomizer 107 b de-randomizes error-correcteddata after ECC processing (ST42 b).

The randomizer and ECC circuit 107 stores de-randomized data in the PBunits 0 to 307 (ST43). Here, the randomizer 107 b writes data back inthe PB units 0 to 307, and ECC-processed data (e.g., error-correcteddata) is stored in the PB units 0 to 263. Since parity data units of PBunits 264 to 307 are not used by the user, ECC-processed data (e.g.,error-corrected data) is not stored in the PB units 264 to 307. Since aunit is not used with respect to a parity data unit of PB units 264 to307, error-corrected data may not be written back or may be writtenback. The PB unit 300 is selected instead of the PB unit 265 under acontrol of a parity column repair circuit 105. By this, error-correctedparity data to be written back in the PB unit 265 is stored in the PBunit 300. A page buffer having an inactive state as a slashed portion inFIG. 19B is not written by a circuit shown in FIG. 28 or 29.

In each PB unit, data Data_i to be written at a memory cell is latchedby a latch unit shown in FIG. 30, so that a sensing operation is ended(ST15). As a selection signal Sel_A is provided to the PB units 0 to255, data stored therein is read through DataBus_(—)1, DataBus_(—)2, andDataBus_(—)3. At this time, a column coding circuit 103 selects the PBunit 256 instead of the PB unit 1 under a control of the column repaircircuit 104. The PB unit 256 outputs data that is data to be written atthe PB unit 1 but data written at the PB unit 256. That is, a defectcolumn is repaired (ST16). As described above, write data written atmemory cell transistors through the PB unit 1 according to a user'srequest is written at another memory cell after repairing. Also, anerror of the written data is corrected and the error-corrected data isoutput from the I/O pad (ST17).

A semiconductor memory device comprises ECC Bus_(—)1˜3 (a first databus); Data Bus_(—)1˜3 (a second data bus) being different in number fromthe first data bus and independent from the first data bus; and a pagebuffer (a data transfer unit), wherein when a data transfer with memorycells is performed at a first mode of operation (an ECC mode), the datatransfer unit connects bit lines, being equal in number to the firstdata bus, from among a plurality of bit lines to the first data bus totransfer data; wherein the data transfer unit comprises a page buffer102 a (a first page buffer) which amplifies a voltage of a bit lineconnected to a normal memory cell and latches the amplified result; apage buffer 102 b (a second page buffer) which is replaced together witha normal memory cell and a bit line when a normal memory cell or a bitline connected to the first page buffer is defective; and a page buffer102 c (a third page buffer) which amplifies a voltage of a bit lineconnected to a parity memory cell and latches the amplified result, andwherein the second data bus is connected to the first and third pagebuffers and the first data bus is connected to the first to third pagebuffers.

The semiconductor memory device further comprises a page buffer 102 d (afourth page buffer) which is connected to the first data bus and isreplaced together with a parity memory cell and a bit line when a paritymemory cell or a bit line connected to the first page buffer isdefective. The semiconductor memory device further comprises a columnrepair circuit 104 (a first repair circuit) which is connected to thesecond data bus and replaces a page buffer, associated with a defectivememory cell or bit line, of the first page buffer with the third pagebuffer. The semiconductor memory device further comprises a paritycolumn repair circuit 105 (a second repair circuit) which is connectedto the first data bus and replaces a page buffer, associated with adefective memory cell or bit line, of the second page buffer with thefourth page buffer. The semiconductor memory device further comprises anECC circuit 107 a which is connected to the first data bus and correctsan error of data from the first and third page buffers based on datafrom the second and fourth page buffers. The semiconductor memory devicefurther comprises a page buffer control circuit which outputs fixed dataas an output of a page buffer, associated with a defective memory cellor bit line, of the first page buffer.

Also, the page buffer control circuit does not allow a write operationfrom the first data bus when a memory cell or a bit line is defective.

Also, the first mode of operation is a mode of operation where inputdata of the ECC circuit is output as output data without repairing on apage buffer, associated with a defective memory cell or bit line, fromamong the first page buffer and the second page buffer used for a repairat the second mode of operation.

Also, when the number of bit lines is n (n being a common multiple of pand q being a natural number, p>q), the first data bus is q, and thesecond data bus is q. If (n/p) address signals are received at the firstmode of operation, the data transfer unit connects p bit lines to the pfirst data bus. If (n/q) address signals are received at the second modeof operation, the data transfer unit connects q bit lines to the seconddata bus. Although the number n of physical bit lines is not a commonmultiple of p and q, the remaining may be used as dummy bit lines.

With the inventive concepts, since it is easy to widen a bus width ofthe ECC bus (e.g., a first data bus) to the ECC circuit 107 (e.g., a buswidth to the ECC circuit being 300 bits), also, a repair circuit (e.g.,a column repair circuit 104) of a main data unit is unnecessary on theECC bus. For this reason, it is possible to implement a high-speed datatransfer at ECC processing. Also, since a size of a repair circuit ofthe main data unit is not increased unlike a conventional technique, anincrease in chip size is suppressed and a cost for fabrication islowered.

Also, in exemplary embodiments, there is described an embodiment wherethere is used a PCR repair system (e.g., a parity column repair circuit105) dedicated to a parity unit having a size smaller than that of arepair circuit of the main data unit. However, the inventive conceptsare not limited thereto. Only, the parity column repair circuit 105 isuseful to repair a defect of the parity unit. In the event that theparity column repair circuit 105 is not used, the error correctioncapacity is damaged. The reason is that an error is corrected byprobability of 50% (0 or 1) per bit of column. In this behalf, asdescribed above, the ECC correction capacity is improved by repairing adefect of the parity unit using the parity column repair circuit 105.

Also, the semiconductor memory device is configured such that the firstmode of operation and the second mode of operation are electricallyswitched. For example, it is possible to write a switching signal (0or 1) through an I/O pad 106 at an operation mode conversion flaginstalled at a nonvolatile memory area (not shown). If the switchingsignal is set to 1, a NAND flash memory 10 is viewed as an EM NANDproduct and operates at the ECC mode (e.g., a first mode of operation).On the other hand, if the switching signal is set to 0, the NAND flashmemory 10 is viewed as a Pure NAND product and operates at the normalmode (e.g., a second mode of operation).

Also, the switching flag is configured such that the switching signal iswritten using a test mode not opened to a user. A maker sets the NANDflash memory 10 to either one of the EM NAND and the Pure NAND using atest mode after the NAND flash memory 10 is fabricated. Therefore,before shipment, the NAND flash memory 10 is set to the Pure NAND havingthe second mode of operation or the EM NAND having the first mode ofoperation and is tested. Or, inventory control is made according to anorder of products. For this reason, it is difficult to improveproductivity.

Below, there is described an embodiment of a semiconductor memory devicewhich is helpful to suppress an increases of chip size, to simplify atest operation and to improve productivity.

Parity Area Open

FIGS. 34A and 34B are diagrams for describing page data associated witha page buffer 102 according to another embodiment of the inventiveconcepts. A page buffer 102 is formed of page buffers 102 a and 102 d asshown in FIG. 24. Here, FIG. 34A shows allocation of column addresses ofPure NAND (e.g., a second mode of operation) in the page buffer 102, andFIG. 34B shows allocation of column addresses of EM NAND (e.g., a firstmode of operation) in the page buffer 102.

In FIG. 34A, there is illustrated a structure of the page buffer 102 atEM NAND. FIG. 34B schematically shows a page buffer 102 a for main data(or, normal data) and spare data and a page buffer 102 b for columnrepair for main data (or, repair data of normal data and spare data).FIG. 34B schematically shows a page buffer 102 c for ECC parity (or,parity data) and a page buffer 102 d for parity's column repair (or,repair data of parity data). spare data of EM NAND, for example, is datasuch as a parity area used for external low-level ECC processing, thenumber of program execution operations performed in a NAND flash memory10, the number of bits corrected by the ECC processing, etc. In a userof the NAND flash memory 10, such data may be valuable informationindicating the lifetime of the NAND flash memory 10. That is, the usermay use an area of a memory array 101 including the page buffer 102 afor normal data and spare data.

Meanwhile, in Pure NAND, as illustrated in FIG. 34A, an area of thememory array 101 including the page buffer 102 c is opened for sparedata, and is used as an area where parity data other than the valuableinformation is stored at ECC processing of an external controllertogether with the area of the memory array 101 including the page buffer102 a.

In FIGS. 34A and 34B, there are illustrated numbers corresponding toeight PB units (e.g., a circuit formed of a PB control circuit and bitinternal circuits 50_0 to 50_7 shown in FIGS. 28 and 29) constitutingthe page buffers 102 a to 102 d. The numbers is Coding shown in FIG.27B, that is, numbers of a selection signal Sel_A or a selection signalSel_B indicating a location of a PB unit.

As illustrated in FIG. 34B, in a NAND flash memory 10 as EM NAND, thepage buffer 102 a includes 8 PB units (hereinafter, referred to as PB8IO units) for normal data and spare data and 1221 PB 8IO units A0 toA2111. The page buffer 102 b has 16 PB 8IO units CR0 to CR15 as the PB8IO units for repair of normal data. The page buffer 102 c 448 PB 8IOunits P0 to P447 as the PB 8IO units for parity data. The page buffer102 d includes 16 PB 8IO units PCR0 to PCR15 as the PB 8IO units forrepair of parity data.

Here, the page buffer 102 c shown in FIG. 34B may use 448 PB 8IO unitsA2012 to A2559 as PB 8IO units for spare data in Pure NAND shown in FIG.34A. That is, the Pure NAND has column addresses A0 to A25559(2048+512). The size of data corresponding to one column address is 1Byte. In the Pure NAND, a pure main data area is A0 to A2047, and anexternal ECC parity area and another information area is theabove-described spare area, which is accessed using column addressesA2048 to A2559.

That is, in the Pure NAND shown in FIG. 34A, a user provides a columnaddress (e.g., A0 to A2559 shown in FIG. 34A) corresponding to theselection signal Sel_A through an I/O pad 106. By this, a column codingcircuit 103 outputs the selection signal Sel_A to the page buffers 102 aand 102 c, and data is accessed through the I/O pad 106. Also, a dataaccess according to an embodiment of the inventive concepts means anoperation where the selection signal Sel_A is provided from the columncoding circuit 103 to a PB control circuit 60 of a page buffer and datais written at a memory cell transistor through a data bus (e.g., asecond data bus) and a bit line connected to the PB control circuit 60and an operation where data is read from a memory cell transistor.

Meanwhile, column addresses A0 to A2047 is allocated to a data unit ofEM NAND like the Pure NAND. But, in case of a spare unit, since a chipincludes an ECC circuit 107 a, external ECC processing is unnecessaryand low-level ECC processing does not need a parity area. Therefore,only 64 B is allocated to a spare area as shown in FIG. 34B. Thus, inthe Pure NAND, an area to which column addresses A2112 to A2559 areallocated may be allocated for internal ECC parity. Also, physically, anarea of the Pure NAND to which column addresses A2112 to A2559 areallocated and an area of the EM NAND to which column addresses P0 toP447 are allocated may have identical memory cells. That is, in the EMNAND shown in FIG. 34B, an area where a column address starts from ‘A’is an area that is accessible by an external device. meanwhile, an areawhere a column address starts from ‘P’ is an area for embedded ECCparity, an area where a column address starts from ‘CR’ is a columnrepair area for main and spare data, and an area where a column addressstarts from ‘PCR’ is a column repair area for embedded ECC parity. Suchareas are inaccessible from the outside of the EM NAND.

That is, in the EM NAND shown in FIG. 34B, a user provides a columnaddress (e.g., A0 to A2111 shown in FIG. 34B) corresponding to theselection signal Sel_A through the I/O pad 106. By this, the columncoding circuit 108 enables a data access to the page buffer 102 athrough the I/O pad 106 using the selection signal Sel_A.

Only, at an access (e.g., a data write operation) of the EM NAND, dataread from memory cell transistors is partially revised by externallyprovided data by a PB control circuit 60 of the page buffer 102 a. AnECC column coding circuit 108 outputs the selection signal Sel_B to thepage buffer 102 a, and data of the page buffer 102 a is provided to arandomizer and ECC circuit 107 through an ECC bus (e.g., a first databus) for randomization and ECC processing. The ECC column coding circuit108 outputs the selection signal Sel_B to the page buffer 102 c, andparity data thus generated is stored in the page buffer 102 c.Afterwards, memory cell transistors are programmed.

Meanwhile, at an access (e.g., a data write operation) of the EM NAND,the ECC column coding circuit 108 outputs the selection signal Sel_B tothe page buffers 102 a and 102 c. by this, data read from memory celltransistors by PB control circuits 60 of the page buffers 102 a and 102c is provided to the randomizer and ECC circuit 107 through an ECC bus(e.g., a first data bus) for ECC processing and de-randomization. TheECC column coding circuit 108 outputs the selection signal Sel_B to thepage buffer 102 a, and the de-randomized (e.g., data after decoding) iswritten at the page buffer 102 a. afterwards, the column coding circuit103 outputs the selection signal Sel_A to the page buffer 102 a, anddata of the page buffer 102 a is output to the exterior through a databus (e.g., a second data bus) and the I/O pad 106.

In a control circuit (not shown in FIG. 24), switching between the PureNAND and the EM NAND is made by a manufacturer after shipment of theNAND flash memory 10. For example, during a test mode not published to auser, data ‘1’ or ‘0’ provided from the exterior through the I/O pad 106may be written at a nonvolatile storage unit (e.g., flag) of a controlcircuit. In the event that the flag stores ‘0’, the control circuitcontrols each circuit such that the NAND flash memory 10 acts as thePure NAND. In the event that the flag stores ‘1’, the control circuitcontrols each circuit such that the NAND flash memory 10 acts as the EMNAND.

That is, in the event that the NAND flash memory 10 is fabricated as thePure NAND, an inaccessible page buffer 102 c of the NAND flash memory 10fabricated as the EM NAND is accessed through a user data accessoperation after shipment.

As described above, column addresses A0 to A2111 are used in common bythe Pure NAND and the EM NAND by changing a spare area of the Pure NANDto a parity unit for embedded ECC. Such changing is limited to a portionfollowing the column address A2111. That is, it is possible to open aparity area for on-chip ECC and to allocate the opened area to a sparearea of a user. For example, the Pure NAND necessitates a spare area forexternal ECC corresponding to about 20% (this value being variable byprocess generation) of a main area. However, since a parity unit of theEM NAND is used, overhead does not arise. With the inventive concepts,it is possible to suppress an increase in a chip area by a sizecorresponding to a spare area. That is, an increase in cost for chipfabrication is suppressed and productivity is improved.

Mask Control Function

Meanwhile, in the EM NAND shown in FIG. 34B, if a user accesses an areaexceeding a usable data area (e.g., column addresses A0 to A2111),embedded ECC parity data is accessed, and data being random with respectto external system is output. This means that the external system isconfused. For this reason, in the event that the user accesses an areaof column addresses P0 to P447 exceeding a usable data area of columnaddresses A0 to A2111, mask control is made as follows.

FIG. 35 is a block diagram schematically illustrating a NAND flashmemory device according to another embodiment of the inventive concepts.FIG. 16 is a diagram schematically illustrating a mask circuit of a NANDflash memory 10 shown in FIG. 35.

In FIG. 35, constituent elements that are identical to those of a NANDflash memory shown in FIG. 24 are marked by the same reference numerals,and a description thereof is thus omitted.

The NAND flash memory 10 shown in FIG. 35 has an address control circuit85 and a mask circuit 86. Although not shown in FIG. 24, the addresscontrol circuit 85 is a circuit that supplies a column address, which auser inputs through an IO pad 106, to a column coding circuit 83, like aconventional technique (shown in FIGS. 44 and 47). In response to acolumn address supplied from the address control circuit 85, the columncoding circuit 83 selects a page buffer unit of a page buffer 102 (e.g.,page buffer units corresponding to A0 to A2559 in FIG. 34) correspondingto the input column address. By this, a PB control circuit 60 of thepage buffer 102 is connected with a data bus, so that data from a memorycell transistor is output to the IO pad 106 or data to be written at amemory cell transistor is received from the IO pad 106.

In addition to the above-descried basic function, the address controlcircuit 85 shown in FIG. 35 includes a well-known comparison circuit. Ifa column address exceeds a final address of a page buffer 102 a, thatis, is A2112, for example, the address control circuit 85 outputs a highlevel of final address signal to the mask circuit 86.

The mask circuit 86 is configured as illustrated in FIG. 36A. That is,as illustrated in FIG. 36A, the mask circuit 86 comprises an invertercircuit 131 and an AND circuit 132. An input of the inverter circuit 131is connected to the comparison circuit of the address control circuit 85to receive the final address signal, and the inverter circuit 131outputs an inverted version of final address signal to a second inputterminal the AND circuit 132. A first input terminal of the AND circuit132 is connected to receive data Clear Data[7:0] that is provided from acolumn repair circuit 104 through a data bus Data_Bus_(—)3 and iserror-free data after ECC processing. An output terminal of the ANDcircuit 132 is connected to the I/O pad 106 through the data busData_Bus_(—)3 as illustrated in FIG. 35.

With the above-described structure, the comparison circuit of theaddress control circuit 85 determines whether a column address reaches adecided final address (e.g., A2111) and outputs the final address signalto the mask circuit 86. By this, in the event that a column addressindicating a page buffer unit is decided as an address following thefinal address (e.g., decided as an address after A2112 indicating afirst page buffer unit of a page buffer 102 c), the mask circuit 86masks data of the page buffer 102 c and outputs fixed data 0 (IO[7:0]=00h).

FIGS. 36B and 36C are operation timing diagrams when a mask controloperation is performed and when a mask control operation is notperformed.

As illustrated in FIG. 36B, in the event that a NAND flash memory 10shown in FIG. 35 performs a burst read operation without a mask controloperation, an internal column address is increased by an external toggleon a column address like FIG. 3. Data IO[8:0] is output to the I/O pad106 at a rise edge of a toggle. Also, the burst read operation is a modeof operation where read data is sequentially output by supplying acolumn address after driving a word line in response to an activecommand at the same time with supplying of a row address.

Here, in EM NAND (e.g., a first mode of operation), since data after acolumn address A2112 is embedded ECC parity data, random data isprovided to an external system. That is, the external system isconfused. As illustrated in FIG. 36C, if a column address reaches anembedded ECC parity area (i.e., a page buffer 102 c), data of the pagebuffer 102 c is masked and fixed data 0 (IO [7:0]=00h) is output. Asdescribed above, in the EM NAND of the inventive concepts, if a readoperation on data exceeding a conventional final address is requested,the such a problem that parity information of ECC processing appears atthe I/O pad 106 regardless of an address space other than auser-accessible area is prevented by the mask control function.

First Redundancy Control Function

In the EM NAND (e.g., a product having a first mode of operation), if aparity area (e.g., a page buffer 102 c) is defective, a defective pagebuffer unit is replaced with a page buffer unit of a page buffer 102 d.In Pure NAND (e.g., a product having a second mode of operation), if adefect exists at the page buffer 102 c, a defective area is opened as aspare data area as described above. For this reason, a repair isperformed by a general redundancy system. In exemplary embodiments,repair techniques on a partial address space (e.g., a parity data area)are different every product. This will be more fully described withreference to FIGS. 37A through 37C.

FIGS. 37A through 37C are diagrams for describing a redundancy controltechnique of a NAND flash memory 10. FIG. 37A shows allocation of pagebuffers repaired according to a first redundancy control technique whena column address is allocated to a page buffer 102 in Pure NAND (e.g., asecond mode of operation). FIG. 37B shows allocation of page buffersrepaired according to a first redundancy control technique when a columnaddress is allocated to a page buffer 102 in EM NAND (e.g., a first modeof operation). Below, a detailed structure is described.

In the Pure NAND, as illustrated in FIG. 37A, defective bits (defect) ofa main data area and a spare data area (e.g., PB 8IO units, bit linesand memory cell transistors selected by column addresses A0 to A2559)are repaired by page buffer units of a page buffer 102 b in the formincluding page buffer units. Also, in this case, a repair on page bufferunits of a page buffer 102 d is not performed. More particular, if PB8IO units A0 to A2559 includes a PB 8IO unit associated with a defectivememory cell or bit line, a column address (A0 to A2559) of the defectivePB 8IO unit is detected at a wafer-level test operation and is writtenat a dedicated area of a memory array 101.

Column addresses (A0 to A2559) of defective PB 8IO units written at thededicated area of the memory array 101 are transferred and latched to acolumn repair circuit 104 of a NAND flash memory 10 at power-up of thePure NAND. As will be described below, a column repair manner isdescribed using an example where a selection system of PB 8IO units iscontrolled. However, the inventive concepts are applicable to awell-known manner where a column is repaired through switching of a databus without selection control of PB 8IO units. At a data read operation,if a column address of a defective PB 8IO unit is received, the columnrepair circuit 104 controls a column coding circuit 103 such that aselection signal Sel_A is not output to the defective PB 8IO unit. Thecolumn coding circuit 103 outputs a selection signal Sel_B for selectinga PB 8IO unit of a page buffer 102 b instead of the defective PB 8IOunit.

As described above, at a data read operation of the Pure NAND, defectivePB 8IO units of the page buffers 102 a and 102 c are not selected by theselection signal Sel_A, and repaired PB 8IO units of the page buffer 102b are selected by the selection signal Sel_A. By this, read dataData_Out_A (e.g., data read from a defective PB 8IO unit) is output toan I/O pad 106 through a data bus (e.g., a second data bus). Also, at adata write operation of the Pure NAND, if write data is received fromthe I/O pad 106, it is provided to a PB 8IO unit of the page buffer 102b corresponding to a repair place through the data bus as write dataData_A_In (e.g., data to be written at the defective PB 8IO unit).

Meanwhile, in EM NAND, as illustrated I FIG. 37B, defective bits(defect) of a main data area and a spare data area (e.g., PB 8IO units,bit lines, and memory cell transistors selected by column addresses A0to A2111) are repaired using page buffer units of the page buffer 102 bin the form including page buffer units. Also, an ECC parity unit (e.g.,PB 8IO units, bit lines, and memory cell transistors selected by columnaddresses P0 to P447) are repaired using page buffer units of the pagebuffer 102 d in the form including page buffer units. That is, in theNAND flash memory 10, an area of the Pure NAND selected by columnaddresses A2112 to A2559 is repaired using an area including the pagebuffer 102 b in case of the Pure NAND and using an area including thepage buffer 102 d in case of the EM NAND.

More particular, if PB 8IO units A0 to A2111 includes a PB 8IO unitassociated with a defective memory cell or bit line, like the Pure NAND,a column address (e.g., max 16 column addresses of A0 to A2111) of thedefective PB 8IO unit is detected at a wafer-level test operation and iswritten at a dedicated area of a memory array 101. A column address(e.g., max 16 column addresses of A0 to A2111) of the defective PB 8IOunit written at a dedicated area of a memory array 101 is transferredand latched to a column repair circuit 104 of a NAND flash memory 10 atpower-up of the EM NAND. At a data write operation, if a column addressof a defective PB 8IO unit is received, the column repair circuit 104controls a column coding circuit 103 such that a selection signal Sel_Ais not output to the defective PB 8IO unit. The column coding circuit103 outputs a selection signal Sel_A for selecting a PB 8IO unit of apage buffer 102 b instead of the defective PB 8IO unit.

Also, if PB 8IO units P0 to P447 (e.g., column address A2112 to A2559 inthe Pure NAND) includes a PB 8IO unit associated with a defective memorycell or bit line, a column address (e.g., max 16 column addresses of P0to P447) of the defective PB 8IO unit is detected at a wafer-level testoperation and is written at a dedicated area of a memory array 101. Acolumn address (e.g., max 16 column addresses of P0 to P447) of thedefective PB 8IO unit written at a dedicated area of a memory array 101is transferred and latched to a parity column repair circuit 105 of aNAND flash memory 10 at power-up of the EM NAND. At an ECC processingoperation, if a column address of a defective PB 8IO unit is received,the parity column repair circuit 105 controls an ECC column codingcircuit 108 such that a selection signal Sel_B is output to thedefective PB 8IO unit. The column coding circuit 103 outputs a selectionsignal Sel_B for selecting a PB 8IO unit of a page buffer 102 d.

At a data write operation of the EM NAND, like the Pure NAND, adefective PB 8IO unit of the page buffer 102 a is not selected by theselection signal Sel_A, and a PB 8IO unit of the page buffer 102 b as arepair place is selected by the selection signal Sel_A. By this, in theEM NAND, if write data is received from the I/O pad 106, it is providedto the PB 8IO unit of the page buffer 102 b corresponding to a repairplace through a data bus as write data Data_A_In (e.g., data to bewritten at the defective PB 81 unit). At ECC encoding, a defective PB8IO unit of the page buffer 102 a outputs fixed data (refer to FIG. 28or 29) to an ECC bus in response to a selection signal Sel_B. Also, a PB8IO unit of the page buffer 102 b outputs data to be written at thedefective PB 8IO unit to the ECC bus in response to the selection signalSel_B. An ECC circuit 107 a and a randomizer 107 b randomize and encodedata received from the ECC bus to generate parity data.

The parity data thus generated is written back at the page buffer 102 c.Assuming a PB 8IO unit of the page buffer 102 c is defective. If anaddress of the defective PB 8IO unit of the page buffer 102 is equal tothe selection signal Sel_B, the parity column repair circuit 105controls the ECC column coding circuit such that a PB 8IO unit of thepage buffer 102 d is selected by the selection signal Sel_B. By this,the parity data is provided to a PB 8IO unit of the page buffer 102 dcorresponding to a pair place as write data Data_B_In (e.g., data to bewritten at a defective PB 8IO unit). Also, the ECC column coding circuit108 outputs the selection signal Sel_B to the defective PB 8IO unit ofthe page buffer 102 c under a control of the parity column repaircircuit 105. But, since data is not written by a circuit shown in FIG.28 or 29, parity data is not updated. Afterwards, programming isexecuted such that data is written at memory cell transistors of thepage buffer 102.

Also, at a data read operation of the EM NAND, first, since decoding andde-randomizing are performed, a PB 8IO unit of the page buffer 102 isselected by the selection signal Sel_B. A defective PB 8IO unit of thepage buffer 102 a outputs fixed data to the ECC bus by a circuit shownin FIG. 28 or 29, and a PB 8IO unit of the page buffer 102 b outputsdata to be written at a defective PB 8IO unit of the original pagebuffer 102 a to the ECC bus. Also, a defective PB 8IO unit of the pagebuffer 102 c outputs fixed data to the ECC bus by a circuit shown inFIG. 28 or 29, and a PB 8IO unit of the page buffer 102 d outputs datato be written at a defective PB 8IO unit of the original page buffer 102c to the ECC bus.

The ECC circuit 107 a and the randomizer 107 b decode and de-randomizedata received from the ECC bus, and write error-corrected data back at aPB 8IO unit of the page buffer 102 a and a PB 8IO unit of the pagebuffer 102 b. Here, the parity column repair circuit 105 does not storea column address of a defective PB 8IO unit of the page buffer 102 athat the column repair circuit 104 stores (here, the parity columnrepair circuit 105 stores a column address of a defective PB 8IO unit ofthe page buffer 102 c). Therefore, under a control of the parity columnrepair circuit 105, the ECC column coding circuit 108 outputs theselection signal Sel_B to a defective PB 8IO unit of the page buffer 102a and a PB 8IO unit of the page buffer 102 b. Only, since a defective PB8IO unit of the page buffer 102 a is configured such that data is notwritten by the selection signal Sel_B, data (e.g., fixed data) is notwritten back. Data to be written back at a defective PB 8IO unit of thepage buffer 102 a is written back at a normal PB 8IO unit of the pagebuffer 102 b corresponding to a repair place.

Afterwards, at a data read operation to the I/O pad 106 of the EM NAND,like the Pure NAND, a defective PB 8IO unit of the page buffer 102 a isnot selected by the selection signal Sel_A, and a PB 8IO unit of thepage buffer 102 b corresponding to a repair place is selected by theselection signal Sel_A. By this, read data Data_Out_A (e.g., data to beread from a defective PB 8IO unit) is output to the I/O pad 106 througha data bus (e.g., a second data bus).

As described above, in a product (on-chip ECC) being the EM NAND, adefect of a parity area including the page buffer 102 c is repairedusing an area for parity repair, that is, an area including the pagebuffer 102 d. However, in a product being the Pure NAND, if an areaincluding the page buffer 102 c is defective, such an area is opened toa user as a spare data area, so that a repair is performed by a generalredundancy system. Thus, a partial address space, that is, repairschemes of the EM NAND and the Pure NAND on a parity area including thepage buffer 102 c are different from each other.

Second Redundancy Control Function

Here, in a product being the Pure NAND, there is described such a mannerthat there is opened an area including the page buffer 102 d as a repairplace when an area including the page buffers 102 a and 102 c isdefective and an area including the page buffer 102 b is expanded. Thatis, in the Pure NAND using a first redundancy control function, there isproposed such a manner that the page buffer 102 d shown in FIG. 37A isnot used but the page buffer 102 d is efficiently utilized in a productbeing the Pure NAND. This will be more fully described with reference toFIG. 37C. FIG. 37C shows allocation of page buffers repaired accordingto a second redundancy control manner when a column address of the PureNAND (e.g., a second mode of operation) is allocated in a page buffer102.

As illustrated in FIG. 37C, in the event that a memory cell including aPB 8IO unit (e.g., a page buffer unit selected by a selection signalSel_A) of PB 8IO units A2112 to A2559 of the Pure NAND is defective, apage buffer 102 d (e.g., PB 8IO units PCR0 to PCR15 shown in FIG. 37B)corresponding to a repair place is opened. The PB 8IO units PCR0 toPCR15 are repaired by PB 8IO units CR16 to CR31 through a column repaircircuit 104.

As will be in detail described below, if a PB 8IO unit, corresponding toa defective memory cell or bit line, of PB 8IO units A0 to A2559 isdefective, a column address (A0 to A2559) of the defective PB 8IO unitis detected at a wafer-level test operation and is written at adedicated area of a memory array 101. A column addresses (A0 to A2559)of defective PB 8IO units written at the dedicated area of the memoryarray 101 is transferred and latched to a column repair circuit 104 of aNAND flash memory 10 at power-up of the Pure NAND.

At a data read operation, if a column address of a defective PB 8IO unitis received, the column repair circuit 104 controls a column codingcircuit 103 such that a selection signal Sel_A is not output to thedefective PB 8IO unit. The column coding circuit 103 outputs a selectionsignal Sel_B for selecting a PB 8IO unit of a page buffer 102 b or apage buffer 102 d instead of the defective PB 8IO unit. Also, inconnection with a data read operation and a data write operation of thePure NAND, a first redundancy control operation is implemented byswitching a repair place into the page buffer 102 b or the page buffer102 d, and a description thereof is thus omitted.

Meanwhile, if PB 8IO units A0 to A2111 includes a PB 8IO unit associatedwith a defective memory cell or bit line, like the Pure NAND, a columnaddress (e.g., max 16 column addresses of A0 to A2111) of the defectivePB 8IO unit is detected at a wafer-level test operation and is writtenat a dedicated area of a memory array 101. A column address (e.g., max16 column addresses of A0 to A2111) of the defective PB 8IO unit writtenat a dedicated area of a memory array 101 is transferred and latched toa column repair circuit 104 of a NAND flash memory 10 at power-up of theEM NAND. At a data write operation, if a column address of a defectivePB 8IO unit is received, the column repair circuit 104 controls a columncoding circuit 103 such that a selection signal Sel_A is not output tothe defective PB 8IO unit. The column coding circuit 103 outputs aselection signal Sel_A for selecting a PB 8IO unit of a page buffer 102b instead of the defective PB 8IO unit.

Also, if PB 8IO units P0 to P447 (e.g., column address A2112 to A2559 inthe Pure NAND) includes a PB 8IO unit associated with a defective memorycell or bit line, a column address (e.g., max 16 column addresses of P0to P447) of the defective PB 8IO unit is detected at a wafer-level testoperation and is written at a dedicated area of a memory array 101. Acolumn address (e.g., max 16 column addresses of P0 to P447) of thedefective PB 8IO unit written at a dedicated area of a memory array 101is transferred and latched to a parity column repair circuit 105 of aNAND flash memory 10 at power-up of the EM NAND. At an ECC processingoperation, if a column address of a defective PB 8IO unit is received,the parity column repair circuit 105 controls an ECC column codingcircuit 108 such that a selection signal Sel_B is output to thedefective PB 8IO unit. The column coding circuit 103 outputs a selectionsignal Sel_B for selecting a PB 8IO unit of a page buffer 102 d.

As described above, in a product being the Pure NAND, there is opened anarea including the page buffer 102 d as a repair place when an areaincluding the page buffers 102 a and 102 c is defective, and an areaincluding the page buffer 102 b is expanded. Therefore, in case of thePure NAND shown in FIG. 37A, only 16 PB 8IO units are used for repairwith respect to column addresses A0 to A2559. But, in case of theinventive concepts, since 32 PB 8IO units are used for repair withrespect to column addresses A0 to A2559, a repair probability isimproved.

Also, a data read operation and a data write operation of the EM NANDfollows the first redundancy control scheme, and a description thereofis thus omitted. Only, as understood from the above description, since acolumn address of a defective PB 8IO unit of an opened page buffer 102 cis duplicatedly stored in both a column repair circuit 104 and a paritycolumn repair circuit 105, an embodiment for bettering such a problemwill be described below.

Address Scan Function

A desirable state of a defective page buffer unit (here, a defective PB8IO unit) viewed as the case that a memory cell transistor or a bit lineconnected thereto is defective is as follows. That is, it is desirableto set defective page buffer units to an inactive state with respect adata unit (e.g., an area including a page buffer 102 a and a page buffer102 c). Also, in page buffer nits of an area including the page buffer102 b and the page buffer 102 d as a repair place, desirably, a pagebuffer unit expanded as a repair place is only activated and a pagebuffer unit not predetermined for repair is inactivated. In other words,it is desirable to minimize the number of page buffer units to beactivated. If a page buffer unit not predetermined for repair is at anactive state, it is a verify target of programming and erasing. Thismeans that a circuit (e.g., a page buffer unit, a bit line, and a memorycell transistor) that need not operate is activated. Thus, the amount ofcurrent consumed is unnecessarily increased. For this reason, it isdesirable to set a page buffer unit that need not operate, to aninactive state. A technique for implementing the above-describeddesirable state will be described below.

In a data unit, inactivation of a defective PB 8IO unit, inactivation ofa page buffer unit, not used for repair, from among page buffer units ofan area including a page buffer 102 b and a page buffer 102 d, andactivation of a page buffer unit expanded as a repair place areimplemented by executing an address scan control operation. Here, theaddress scan control operation is an operation of converting information(e.g., a data write signal Data_In_A or Data_In_B shown in FIG. 28 or29) indicating whether a page buffer unit is defective into a columnaddress (e.g., a selection signal Sel_A or Sel_B) and transferring thecolumn address to a PB control circuit 60 shown in FIG. 28 or 29.

Below, an address scan control technique is described with reference toFIGS. 38A through 40. FIGS. 38A and 38B are flow charts of an addressscan control method. FIG. 39 is a timing diagram of an address scancontrol operation. FIG. 40 is a diagram schematically illustrating anaddress map of a column address Add_B.

Here, a circuit being an address scan control target is a PB controlcircuit 60 (e.g., a circuit shown in FIG. 28 or 29) of each page bufferunit. Below, the inventive concepts are described under the assumptionthat the PB control circuit 60 shown in FIG. 28 is a circuit being anaddress scan control target. Also, it is assumed that in the PB controlcircuit 60 shown in FIG. 28, an output terminal of an inverter circuit62 and a gate terminal of a transistor 94 are short-circuited and anoutput terminal of an inverter circuit 63 and a gate terminal of atransistor 95 are short-circuited. That is, referring to the PB controlcircuit 60, in the event that a power-on reset signal POR_Mode has ahigh level, write signals DI and nDI, defect information signals SDI andnSDI and defect signals PB_Defect and nPB_Defect have the followingrelation. That is, when the write signal DI goes to a high level (thewrite signal nDI maintaining a low level), the defect information signalSDI goes to a high level (the defect information signal nSDI maintaininga low level), the defect signal PB_Defect goes to a low level, and thedefect information signal nPB_Defect goes to a high level. Thiscondition of the signals means that the PB control circuit 60 is good.Meanwhile, the write signal DI maintains a low level (the write signalnDI going to a high level), the defect information signal SDI maintainsto a low level (the defect information signal nSDI going to a highlevel), the defect signal PB_Defect goes to a high level, and the defectinformation signal nPB_Defect goes to a low level. This condition of thesignals means that the PB control circuit 60 is bad.

Also, there is described Add_A Scan where information indicating whethera page buffer unit is defective is converted to a selection signal Sel_Awith respect to a page buffer unit (here, a PB 8IO unit shown in FIG.37A) of a column address (hereinafter, referred to as ADD_A). Moreparticular, Add_A Scan is executed under a condition of the followingcircuit operation.

That is, an address control circuit 85 shown in FIG. 35 increments acolumn address ADD_A[11:0] from an initial value (e.g., all ‘0’: 00h) insynchronization with a rising edge of a clock signal Add_CLK providedfrom a control circuit (not shown) or an external device.

Also, the address control circuit 85 outputs the column addressADD_A[11:0] to a column repair circuit 104. The column repair circuit104 compares the column address ADD_A[11:0] with defect bit information(e.g., a defect column address ADD_A of a defective PB 8IO unit) storedbefore execution of an address scan operation

Based on the comparison result, the column repair circuit 104 controls acolumn coding circuit 103 to output a selection signal Sel_A to a PB 8IOunit.

Also, the column repair circuit 104 outputs a write enable signalfDinEnable and write data Data_In_A to a PB 8IO unit corresponding to acolumn address ADD_A in synchronization with a rising edge of a clocksignal DIn_CLK received from a control circuit (not shown) or anexternal device. Also, a control circuit (not shown) may provide thewrite enable signal fDinEnable, a data input circuit connected to theI/O circuit 106 may provide the write data Data_In_A, or an externaltester may provide the write data Data_In_A through the I/O pad 106.Also, a period of the clock signal DIn_CLK is equal to that of a clocksignal ADD_CLK, and a rising edge and a falling edge are delayed by aquarter of a period.

That is, the column coding circuit 103 is controlled by the columnrepair circuit 104 according to a comparison result of the column repaircircuit 104, and outputs a selection signal Sel_A to a PB 8IO unit.Also, the column repair circuit 104 outputs write data Data_In_A to a PB8IO unit, based on its own comparison result.

An embodiment where Add_A Scan on Pure NAND shown in FIG. 37A isexecuted is described using a flow chart shown in FIGS. 38A and 38B anda timing diagram shown in FIG. 39. Also, in FIG. 39, “DATA PBAdd_A=001h” is a PB 8IO unit A1 of a page buffer 102 a shown in FIG.37A, and “CR [0]PB” is a PB 8IO unit CR0 of a page buffer 102 b shown inFIG. 37A.

Here, a PB 8IO unit A1 of the page buffer 102 a is a defective pagebuffer unit and is inactivated by Add_A Scan. Other PB 8IO units A0 andA2 to A2559 are activated by Add_A Scan. Also, a PB 8IO unit CR0 of thepage buffer 102 b is inactivated by Add_A Scan, and other PB 8IO unitsCR1 to CR15 are activated by Add_A Scan.

Also, it is necessary to prepare defect bit information (here, a defectcolumn address ADD_A′=001h being an address of a defective PB 8IO unitA1) before execution of Address Scan. In general, the defect bitinformation is stored in a nonvolatile system area. When a power issupplied or an external specific command (e.g., a reset command, etc.)is received, the defect bit information is transferred to the columnrepair circuit 104 (or, a parity column repair circuit 105 in case ofAdd_B Scan). Here, it is assumed that at power-up, a power-on resetsignal POR_Mode goes to a high level and the defect column addressADD_A′=001h is transferred to the column repair circuit 104.

Also, the column repair circuit 104 controls the column coding circuit103 to sequentially output a selection signal Sel_A synchronized with arising edge of the clock signal Add_CLK to PB 8IO units A0 to A2559.Meanwhile, during an interval of Add_A Scan, the column repair circuit104 controls the column coding circuit 103 to continue to output a highlevel of selection signal Sel_A to PB 8IO units CR0 to CR15. Also, thecolumn repair circuit 104 outputs the write enable signal fDinEnable tothe PB 8IO units A0 to A2559 in synchronization with a rising edge ofthe clock signal DIn_CLK. Meanwhile, the column repair circuit 104 setsto a low level as a default state the write enable signal fDinEnablewith respect to the PB 8IO units CR0 to CR15, during an interval ofAdd_A Scan. However, in the event that a comparison result indicates‘MISS’, the column repair circuit 104 outputs write enable signalfDinEnable to the PB 8IO units CR0 to CR15 in synchronization with arising edge of the clock signal DIn_CLK.

First, at power-up, a control circuit (not shown) or a power-on resetsignal generating circuit outputs a high level of power-on reset signalPOR_Mode. Also, the power-on reset signal POR_Mode has a high levelduring an interval of Add_A Scan such that a transistor 96 of a PBcontrol circuit 60 is turned on. At t1, the address control circuit 85outputs a column address ADD_A [11:0]=000h (e.g., an initial value) tothe column repair circuit 104 in synchronization with a rising edge ofthe clock signal Add_CLK (ST51 shown in FIGS. 38A).

The column repair circuit 104 compares the input column address ADD_A[11:0] and a defect column address ADD_A′ (ST52). Here, the columnrepair circuit 104 outputs a comparison result indicating that the inputcolumn address ADD_A [11:0] is not equal to the defect column addressADD_A′=001 h.

Also, when the input column address ADD_A [11:0] is not equal to thedefect column address ADD_A′=001h, the column repair circuit 104maintains write data Data_In_A at a low level. Also, the column repaircircuit 104 controls the column coding circuit 103 such that a selectionsignal Sel_A provided to a PB 8IO unit A0 transitions to a high level.That is, the PB 8IO unit A0 is selected. Also, the write enable signalfDinEnable transitions to a high level under a control of the columnrepair circuit 104.

By this, a PB control circuit 60 of the PB 8IO unit A0 latches a lowlevel of defect signal PB_Defect (indicating that the PB 8IO unit A0 isgood) (not shown in FIG. 39). That is, in a product being Pure NAND, thePB 8IO unit A0 is activated. That is, if selected by the column codingcircuit 103, it is possible to receive write data Data_In_A at a datawrite operation and to output read data Data_Out_A.

Meanwhile, in a PB 8IO unit of PB 8IO units CR0 to CR15, the writeenable signal fDinEnable maintains a low level. Therefore, the PBcontrol circuit 60 of each PB 8IO unit latches a high level (e.g., adefault state) of defect signal PB_Defect. The default state isimplemented by such a manner that the column repair circuit 104 controlsthe column coding circuit 103 to supply a high level of selection signalSel_A or a high level of write data Data_In_A and a high level of writedata Data_In_A to the PB 8IO units CR0 to CR15 in a lump prior to astart of Add_A Scan.

Then, in the column repair circuit 104, if a comparison result indicates‘MISS’, the procedure goes to step ST55 (No). Then, the address controlcircuit 85 determines whether a column address Add_A output to thecolumn repair circuit 104 is equal to a final address (e.g., a finalcolumn address Final_Add_A) (ST55). Here, since Final_Add_A=9FFh(=2559),the procedure goes to step ST56 (ST55—No) as a consequence ofdetermining that the column address Add_A output to the column repaircircuit 104 is not equal to a final address. The address control circuit85 increments a column address Add_A output to the column repair circuit104 by 1 (00h) (ST56). Here, the column address Add_A=000h isincremented by 1, and the column address Add_A[11:0]=001h is output tothe column repair circuit 104.

Then, the column repair circuit 104 compares the input column addressAdd_A[11:0] and the defect column address ADD_A′ (ST52). Here, the inputcolumn address Add_A[11:0]=001h is equal to the defect column addressADD_A′=001h. Thus, the procedure goes to step ST53 (Yes).

Then, the column repair circuit 104 inactivates a PB 8IO unit of a pagebuffer 102 a corresponding to the defect address ADD_A′ (ST53). Here,since both addresses are equal to each other, write data Data_In_Atransitions from a low level to a high level under a control of thecolumn repair circuit 104 (t2 shown in FIG. 39). Also, the column repaircircuit 104 controls the column coding circuit 103 such that theselection signal Sel_A provided to a PB 8IO unit A1 transitions to ahigh level for selection of the PB 8IO unit A1. Also, the column repaircircuit 104 sets the write enable signal fDinEnable to a high level. Bythis, the PB control circuit 60 of the PB 8IO unit A1 latches a highlevel of defect signal PB_Defect (indicating that the PB 8IO unit A0 isbad). That is, in a product being the Pure NAND, the PB 8IO unit A1 isinactivated. That is, since not selected by the column coding circuit103, write data Data_In_A is not received at a data write operation andread data Data_Out_A is not output at a data read operation.

Also, the column repair circuit 104 activates a PB 8IO unit of the pagebuffer 102 b as a repair place of a PB 8IO unit of the page buffer 102 acorresponding to the defect column address ADD_A′ (ST54). First, sinceboth addresses are equal to each other, the column repair circuit 104maintains a low level of write data Data_In_A (ST52). Also, under acontrol of the column repair circuit 104, the write enable signalfDinEnable supplied to a PB 8IO unit CR0 transitions to a high level. Bythis, the PB control circuit 60 of the PB 8IO unit CR0 latches a lowlevel of detect signal PB_Defect (indicating that the PB 8IO unit CR0 isgood). That is, in a product being the Pure NAND, the PB 8IO unit CR0 isactivated. That is, the column coding circuit 103 selects a PB 8IO unitA1 as a repair place. In a data write operation, write data Data_In_A tobe written at an original PB 8IO unit A1 is received. At a data readoperation, read data Data_In_A to be read from an original PB 8IO unitA1 is output.

Operations of the above-described steps ST56 and ST52 to ST54 areiterated until in the address control circuit 85, a column address Add_Aoutput to the column repair circuit 104 is equal to a final address(e.g., a final column address Final_Add_A). If a column address Add_Aoutput to the column repair circuit 104 is equal to a final addressFinal_Add_A=9FFh(=2559), Add_A Scan is ended (ST55—Yes).

With the above-described Add_A Scan, in the Pure NAND, according to astate of a defective PB 8IO unit, defective page buffer units of a dataunit (e.g., an area including page buffers 102 a and 102 c) are allinactivated. Also, in page buffer units of an area including the pagebuffer 102 b as a repair place, page buffer units to be expanded as arepair place are only activated. In this case, page buffer units notpredetermined for repair are inactivated.

Also, as described above, in the Pure NAND, coding (e.g., selection of apage buffer unit) and repairing of a defective page buffer unit (e.g.,repairing using a page buffer unit of the page buffer 102 b) are made bythe column coding circuit 103, the column repair circuit 104, and theaddress control circuit 85 shown in FIG. 28. Also, by Add_A Scan, asdescribed above, defective page buffer units are all inactivated, andpage buffer units not predetermined for repair are inactivated. A systemof the inventive concepts is configured such that electrical switchingbetween the Pure NAND and the EM NAND is made using a productinformation bit of the Pure NAND and the EM NAND. In the EM NAND, coding(e.g., selection of a page buffer unit) and repairing of a defectivepage buffer unit (e.g., repairing using a page buffer unit of the pagebuffer 102 d) are made by the ECC column coding circuit 108, the repaircolumn repair circuit 105, and the randomizer and ECC circuit 107 shownin FIG. 28. Also, by Add_B Scan, as described above, defective pagebuffer units are all inactivated, and page buffer units notpredetermined for repair are inactivated.

Individual Scanning on Column Addresses Add_A and Add_B

In the EM NAND, each page buffer unit is selected based on an addressmap of column addresses Add_B shown in FIG. 40. As illustrated in FIG.40, in the EM NAND, it is possible to select PB 8IO units A0 to A2111(PB 8IO units of a page buffer 102 a) and PB 8IO units CR0 to CR15 (PB8IO units of a page buffer 102 c) shown FIG. 37B using a column addressAdd_B.

Add_B Scan of the Pure NAND is described using a flow chart shown inFIG. 38B so as to correspond to Add_A Scan of the Pure NAND shown inFIG. 38A. Also, there is described an embodiment where Add_A Scan isperformed under a condition of Add_A=2111 and Add_B Scan is performedunder a condition of Add_B=15. Since the Pure NAND and the EM NAND areelectrically switched, at a test operation before shipment, Add_A Scanon an operation associated with a data unit A0 to A2111 (e.g., PB 8IOunits A0 to A2111) of the Pure NAND is executed, and Add_B Scan isexecuted after switching into the EM NAND. In Add_B Scan, a defectiveparity PB (e.g., a defective PB 8IO unit) of a parity unit P0 to P447(e.g., PB 8IO units CR0 to CR447) are inactivated, and PCR (PB 8IO unitsPCR0 to PCR15 of the page buffer 102 d) being a repair target isactivated.

Also, Add_B Scan is executed under a condition of the following circuitoperation so as to correspond to the Pure NAND. That is, a randomizerand ECC circuit 107 shown in FIG. 35 increments a column addressADD_A[3:0] from an initial value (e.g., all ‘0’: 00h) in synchronizationwith a rising edge of a clock signal Add_CLK provided from a controlcircuit (not shown). Also, the randomizer and ECC circuit 107 outputsthe column address ADD_A[3:0] to a parity column repair circuit 105. Theparity column repair circuit 105 compares the column address ADD_A[3:0]with defect bit information (e.g., a defect column address ADD_B′ of adefective PB 8IO unit) stored before execution of an address scanoperation

Based on the comparison result, the parity column repair circuit 105controls an ECC column coding circuit 108 to output a selection signalSel_B to a PB 8IO unit. Also, the parity column repair circuit 105outputs a write enable signal fDinEnable and write data Data_In_B to aPB 8IO unit corresponding to a column address ADD_B in synchronizationwith a rising edge of a clock signal DIn_CLK received from a controlcircuit (not shown). Also, a control circuit (not shown) may provide thewrite enable signal fDinEnable or an external tester may provide thewrite data Data_In_B through the I/O pad 106. Also, a period of theclock signal DIn_CLK is equal to that of a clock signal ADD_CLK, and arising edge and a falling edge are delayed by a quarter of a period.That is, the ECC column coding circuit 108 is controlled by the paritycolumn repair circuit 105 according to a comparison result of the paritycolumn repair circuit 105, and outputs a selection signal Sel_B to a PB8IO unit. Also, the parity column repair circuit 105 outputs write dataData_In_B to a PB 8IO unit, based on its own comparison result.

An embodiment where Add_A Scan on EM NAND shown in FIG. 37B is executedis described using a flow chart shown in FIG. 38B. Here, a PB 8IO unitA1 of the page buffer 102 a is a defective page buffer unit and isinactivated by Add_A Scan. Other PB 8IO units A0 and A2 to A2111 areactivated by Add_A Scan. Also, a PB 8IO unit CR0 of the page buffer 102b is activated by Add_A Scan, and other PB 8IO units CR1 to CR15 areinactivated by Add_A Scan. Also, like the Pure NAND, it is necessary toprepare defect bit information (here, a defect column address ADD_B′being a column address of a defective PB 8IO unit P0 to P447 of a pagebuffer 102 c) before execution of Address Scan. In general, the defectbit information is transferred to the parity column repair circuit 105in case of Add_B Scan. Here, it is assumed that at power-up, a power-onreset signal POR_Mode goes to a high level and the defect column addressADD_B′ is transferred to the parity column repair circuit 105.

Also, the parity column repair circuit 105 controls the ECC columncoding circuit 108 to sequentially output a selection signal Sel_Bsynchronized with a rising edge of the clock signal Add_CLK to PB 8IOunits P0 to P447. Meanwhile, during an interval of Add_B Scan, theparity column repair circuit 105 controls the ECC column coding circuit108 to continue to output a high level of selection signal Sel_B to PB8IO units PCR0 to PCR15. Also, the parity column repair circuit 105outputs the write enable signal fDinEnable to the PB 8IO units A0 toA2111 and P0 to P447 in synchronization with a rising edge of the clocksignal DIn_CLK. Meanwhile, the parity column repair circuit 105 sets toa low level as a default state the write enable signal fDinEnable withrespect to the PB 8IO units PCR0 to PCR15 as a repair place, during aninterval of Add_B Scan. However, in the event that a comparison resultindicates ‘HIT’, the column repair circuit 104 outputs write enablesignal fDinEnable to the PB 8IO units PCR0 to PCR15 in synchronizationwith a rising edge of the clock signal DIn_CLK.

First, at power-up, a control circuit (not shown) or a power-on resetsignal generating circuit outputs a high level of power-on reset signalPOR_Mode. Also, the power-on reset signal POR_Mode has a high levelduring an interval of Add_B Scan such that a transistor 96 of a PBcontrol circuit 60 is turned on. The randomizer and ECC circuit 107outputs a column address ADD_B [3:0]=000h (e.g., an initial value) tothe parity column repair circuit 105 in synchronization with a risingedge of the clock signal Add_CLK (ST61 shown in FIGS. 38B).

The parity column repair circuit 105 compares the input column addressADD_B [3:0] and a defect column address ADD_B′ (ST62). Here, the columnrepair circuit 104 outputs a comparison result indicating that the inputcolumn address ADD_B[3:0]=000h is not equal to the defect column addressADD_B′.

Also, when both addresses are not equal to each other, the parity columnrepair circuit 105 maintains write data Data_In_B at a low level. Also,the parity column repair circuit 105 controls the ECC column codingcircuit 108 such that a selection signal Sel_B provided to a PB 8IO unitB0 (e.g., PB 8IO units A0, A16 to A2096, P0, and P16 to P432)transitions to a high level. That is, the PB 8IO unit B0 is selected.Also, the write enable signal fDinEnable transitions to a high levelunder a control of the parity column repair circuit 105. Only, theparity column repair circuit 105 maintains the write enable signalfDinEnable provided to PB 8IO units A0 and A16 to A2096 at a low level.The reason is that their PB 8IO units are previously activated orinactivated by Add_A Scan.

By this, in PB control circuits 60 of the PB 8IO unit P0 and P16 to P432of the PB 8IO unit B0, there is latched a low level of defect signalPB_Defect (indicating that the PB 8IO unit P0 and P16 to P432 are good).That is, in a product being EM NAND, the PB 8IO unit P0 and P16 to P432of the PB 8IO unit B0 is activated. That is, if selected by the ECCcolumn coding circuit 108, it is possible to receive write dataData_In_B at a parity data write operation of ECC processing and tooutput read data Data_Out_B at a parity data read operation of ECCprocessing.

Meanwhile, in a PB 8IO unit of PB 8IO units PCR0 to PCR15, the writeenable signal fDinEnable maintains a low level. Therefore, the PBcontrol circuit 60 of each PB 8IO unit latches a high level (e.g., adefault state) of defect signal PB_Defect. The default state isimplemented by such a manner that the parity column repair circuit 105controls the ECC column coding circuit 108 to supply a high level ofselection signal Sel_B and a high level of write data Data_In_B and ahigh level of write data Data_In_B to the PB 8IO units PCR0 to PCR15 ina lump prior to a start of Add_B Scan.

Then, in the parity column repair circuit 105, if a comparison resultindicates ‘MISS’, the procedure goes to step ST62 (No). Then, therandomizer and ECC circuit 107 determines whether a column address Add_Boutput to the parity column repair circuit 105 is equal to a finaladdress (e.g., a final column address Final_Add_B) (ST55). Here, sinceFinal_Add_A=00Fh(=15), the procedure goes to step ST66 (ST55—No) as aconsequence of determining that the column address Add_B is not equal tothe final address. The randomizer and ECC circuit 107 increments acolumn address Add_A output to the parity column repair circuit 105 by 1(00h) (ST66). Here, the column address Add_B=000h is incremented by 1,and the column address Add_B[3:0]=001h is output to the parity columnrepair circuit 105.

Then, the parity column repair circuit 105 compares the input columnaddress Add_B[3:0] and the defect column address ADD_B′ (ST62). Here,the input column address Add_B[11:0]=001h is determined to be equal tothe defect column address ADD_B′. Thus, the procedure goes to step ST63(ST62—Yes).

Then, the parity column repair circuit 105 inactivates a PB 8IO unit ofa page buffer 102 c corresponding to the defect address ADD_B′(ST63).Here, since both addresses are equal to each other, in a PB 8IO unit ofthe page buffer 102 c corresponding to the defect column address ADD_B′,write data Data_In_B transitions from a low level to a high level undera control of the parity column repair circuit 105. Also, the paritycolumn repair circuit 105 controls the ECC column coding circuit 108such that the selection signal Sel_B provided to a PB 8IO unit B1 (PB8IO units A1 and A17 to A2097, P1 and P17 to P433 shown in FIG. 40)transitions to a high level for selection of the PB 8IO unit A1. Also,the column repair circuit 104 sets the write enable signal fDinEnable toa high level for selection of the PB 8IO unit B1. Also, the paritycolumn repair circuit 105 makes the write enable signal fDinEnabletransition to a high level. Only, the parity column repair circuit 105maintains the write enable signal fDinEnable provided to the PB 8IOunits A1 and A17 to A2097 at a low level. The reason is that their PB8IO units are previously activated or inactivated by Add_A Scan.

By this, in the PB control circuit 60 of the PB 8IO unit of the pagebuffer 102 c corresponding to the defect column address ADD_B′, there islatched a high level of defect signal PB_Defect (indicating that the PB8IO unit is bad). That is, in a product being the EM NAND, the PB 8IOunit A1 of the page buffer 102 c corresponding to the defect columnaddress ADD_B′ is inactivated. That is, since not selected by the ECCcolumn coding circuit 108, write data Data_In_B is not received at adata write operation and fixed data is output as read data Data_Out_B ata data read operation.

Also, the parity column repair circuit 105 activates a PB 8IO unit ofthe page buffer 102 d as a repair place of a PB 8IO unit of the pagebuffer 102 c corresponding to the defect column address ADD_B′ (ST64).First, since both addresses are equal to each other, the parity columnrepair circuit 105 maintains a low level of write data Data_In_B (ST62).Also, under a control of the parity column repair circuit 105, the writeenable signal fDinEnable supplied to a PB 8IO unit PCR0 transitions to ahigh level.

By this, the PB control circuit 60 of the PB 8IO unit PCR0 latches a lowlevel of detect signal PB_Defect (indicating that the PB 8IO unit PCR0is good). That is, in a product being the EM NAND, the PB 8IO unit PCR0is activated. That is, the ECC column coding circuit 108 selects a PB8IO unit of the page buffer 102 c corresponding to the defect columnaddress ADD_B′ as a repair place. In a data write operation, write dataData_In_B to be written at a PB 8IO unit of an original page buffer 102c is received. At a data read operation, read data Data_In_B to be readfrom a PB 8IO unit of an original page buffer 102 c is output.

Operations of the above-described steps ST66 and ST62 to ST64 areiterated until in the randomizer and ECC circuit 107, a column addressAdd_B output to the parity column repair circuit 105 is equal to a finaladdress (e.g., a final column address Final_Add_B). If a column addressAdd_B output to the parity column repair circuit 105 is equal to a finaladdress Final_Add_B=00Fh(=15), Add_B Scan is ended (ST65—Yes).

With the above-described Add_B Scan, in the EM NAND, according to astate of a defective PB 8IO unit, defective page buffer units of a dataunit (e.g., an area including the page buffer 102 a) and a parity unit(e.g., area including the page buffer 102 c) are all inactivated. Also,in page buffer units of an area including the page buffer 102 c as arepair place, page buffer units to be expanded as a repair place areonly activated. In this case, page buffer units not predetermined forrepair are inactivated.

In case of the above-described address scan operation, at aninitialization sequence after power-on, defect bit information stored ina nonvolatile system area is transferred to the column repair circuit104 at Add_A Scan and to the parity column repair circuit 105 at Add_BScan. FIGS. 41A and 41B are diagrams schematically illustrating anembodiment where stored defect bit information is transferred. FIG. 41Ashows an embodiment where stored defect bit information is transferredat the above-described address scan operation.

As illustrated in FIG. 41A, the column repair circuit 104 has Defect BitLatch (A0 A2559) (hereinafter, referred to as a latch circuit) 104L thatstores defect bit information at Add_A Scan. Here, the defect bitinformation at Add_A Scan may be column addresses (e.g., a plurality ofbit information of A0 to A2559) of defective PB 8IO units of pagebuffers 102 a and 102 c in Pure NAND shown in FIG. 37A. Also, the paritycolumn repair circuit 105 has Defect Bit Latch (P0 P447) (hereinafter,referred to as a latch circuit) 105L that stores defect bit informationat Add_B Scan. Here, the defect bit information at Add_B Scan may becolumn addresses (e.g., a plurality of bit information of P0 to P447) ofdefective PB 8IO units of the page buffer 102 c in EM NAND shown in FIG.37B.

Also, a nonvolatile system area 102 b 1 stores defect bit informationobtained through Add_A Scan, that is, a result of a test operation on aNAND flash memory 10 performed to detect a column address (e.g., aplurality of bit information of A0 to A2559) of a defective PB 8IO unitwith it being electrically switched into a Pure NAND product. Also, thenonvolatile system area 102 b 1 is formed of some blocks of a memoryarray 101 of the NAND flash memory 10, for example.

Also, a nonvolatile system area 102 b 2 stores defect bit informationobtained through Add_B Scan, that is, a result of a test operation on aNAND flash memory 10 performed to detect a column address (e.g., aplurality of bit information of P0 to P447) of a defective PB 8IO unitwith it being electrically switched into an EM NAND product. Also, likethe nonvolatile system area 102 b 1, the nonvolatile system area 102 b 2is formed of some blocks of the memory array 101 of the NAND flashmemory 10, for example.

In the event that there is selected such a manner that an address scanoperation is independently performed with respect to the above-describedcolumn addresses Add_A and Add_B, defect bit information at execution ofAdd_A Scan is stored in the nonvolatile system area 102 b 1, and defectbit information at execution of Add_B Scan is stored in the nonvolatilesystem area 102 b 2. Also, defect bit information at execution of Add_AScan and defect bit information at execution of Add_B Scan aretransferred to the column repair circuit 104 and the parity columnrepair circuit 105, respectively.

With the above-described manner, Referring to FIGS. 37A and 37B, in theevent that a PB 8IO unit A2112 of the Pure NAND using a column addressAdd_A is defective, a PB 8IO unit P0 of the EM NAND using a columnaddress Add_B being the physically same PB 8IO unit is defective. Inthis case, with respect to a physically same defect, two addresses, thatis, the defect column address Add_A and the defect column address Add_Bare respectively stored in two areas, that is, the nonvolatile systemarea 102 b 1 and the nonvolatile system area 102 b 2 as defectinformation. It is possible to simplify a test process where defect bitinformation is detected and stored before shipment by focusing defectinformation on the nonvolatile system area 102 b 1.

FIG. 41B is a diagram showing such a state that defect bit informationis focused on mapping of a column address Add_A. Here, at a transfer tothe parity column repair circuit 105, mapping information of a columnaddress Add_A is converted to mapping information of a column addressAdd_B by a detect bit information conversion circuit 110. In both thePure NAND and the EM NAND, since defect bit information is focused on acolumn address Add_A, it is possible to simplify a test process wheredefect bit information is detected and stored before shipment.

Below, such a manner that an address scan operation is completed only byAdd_A Scan is described.

Manner of Completion Only Using Add_A Scan

In case of such a manner that an address scan operation is independentlyperformed with respect to the above-described column addresses Add_A andAdd_B, address scan operations Add_A Scan and Add_B Scan are performedevery address mapping. However, there is proposed an Add_A Scan-focusedsystem. For ease of description, it is assumed that a NAND flash memory10 is configured to include a column redundancy (CR) structure of PureNAND shown in FIG. 37C. In the NAND flash memory 10, a latch circuit104L of a column repair circuit 104 shown in FIGS. 41A and 41B latchesdefect column address information Add_A from A0 to A2559 regardless ofwhether the NAND flash memory 10 is set to the Pure NAND or to the EMNAND.

FIG. 42 is a diagram showing a transfer path of defect bit informationfrom a latch circuit 104L of a column repair circuit 104 to a PB 8IOunit. Referring to FIG. 42, a latch circuit 104L is a component forlatch defect information, and has latches respectively corresponding toPB 8IO units CR0 to CR15 and latches respectively corresponding to PB8IO units PCR0 to PCR15. A latch corresponding to each unit comprises anaddress information storing unit to store a column address of a defectbit and an enable bit storing unit indicating whether to repair a defectbit. In exemplary embodiments, a latch corresponding to each unitfurther comprises an IO information storing unit to latch defect IOinformation. In case of the Pure NAND shown in FIG. 37C, a latchcorresponding to each of the PB 8IO units CR0 to CR15 stores defect bitinformation of a column address A0 to A2111, and a latch correspondingto each of the PB 8IO units PCR0 to PCR15 stores defect bit informationof A2112 to A2559.

As described above, during an address scan operation, if defect bitinformation is equal to a column address Add_A provided to the columnrepair circuit 104, a comparison result signal CR Hit being a comparisonresult of a comparison circuit of the column repair circuit 104 shown inFIG. 42 goes to a high level. By this, each driver (e.g., a page bufferdriver) of the column repair circuit 104 transfers defect bitinformation (e.g., a write enable signal fDinEnable) to each PB 8IOunit.

With the above structure, it is possible to transfer defect informationindicating whether to activate or inactivate to corresponding CR/PCR byperforming the above-described Add_A Scan operation within a range fromA0 to A2559. Also, it is possible to use the same scan manner (e.g.,Add_A Scan) regardless of whether the NAND flash memory 10 is switchedto the EM NAND or to the Pure NAND. Thus, it is possible to shorten atest time after fabrication and to improve productivity.

Another Manner of Completion Only Using Add_A Scan

In an embodiment described with reference to FIG. 42, a column repaircircuit 104 need include a component that stores defect bit informationof PB 8IO units CR0 to CR15 and PB 8IO units PCR0 to PCR15. However thecolumn repair circuit 104 may be bettered by increasing the number oflatches. This will be more fully described below. In exemplaryembodiments, at initialization (e.g., power-on), a manner of selecting apage buffer unit (e.g., a PB IO unit) as a target to which defectinformation is transferred at an address scan operation, based onelectrical information indicating whether to use an on-chip ECC (i.e.,information indicating whether a NAND flash memory 10 is switched intoPure NAND or into EM NAND).

There is described an embodiment where the inventive concepts areapplied to the Pure NAND shown in FIG. 37A. The Pure NAND shown in FIG.14A may be a system where PB 8IO units CR0 to CR15 of a page buffer 102b are used as a repair place with respect to PB 8IO units A2112 toA2559.

FIGS. 43A and 43B are diagrams showing a transfer path of defect bitinformation from a latch circuit 104L of a column repair circuit 104 toa PB 8IO unit according to another embodiment of the inventive concepts.

As illustrated in FIG. 43A, as compared with FIG. 42, latches for defectbit information of PB 8IO units PCR0 to PCR15, comparison circuits andPB drivers are eliminated. Here, selection signals YPCR and YCR may beselection signals of PB control circuits 60. The selection signal YPCRis connected to a terminal of a selection signal Sel_A of PB controlunits 60 of the PB 8IO units PCR0 to PCR15, and the selection signal YCRis connected to a terminal of the selection signal Sel_A of PB controlunits 60 of the PB 8IO units CR0 to CR15 (refer to 28 or 29). That is,it is possible to control whether to select a PB 8IO unit of a pagebuffer 102 b or a PB 8IO unit of a page buffer 102 d by using one of theselection signals YPCR and YCR.

As illustrated in FIG. 43B, whether to use the selection signal YPCR orthe selection signal YCR is decided according to an address (e.g., acolumn address) and a product. In the event that the NAND flash memory10 is Pure NAND, the selection signal YCR is provided to a terminal ofthe selection signal Sel_A of the PB control units 60 of the PB 8IOunits CR0 to CR15 as a repair place. Meanwhile in the event that theNAND flash memory 10 is EM NAND, the selection signal YCR is provided toa terminal of the selection signal Sel_A of the PB control units 60 ofthe PB 8IO units CR0 to CR15 as a repair place with respect to PB 8IOunits A0 to A2111. Also, the selection signal YPCR is provided to aterminal of the selection signal Sel_A of the PB control units 60 of thePB 8IO units PCR0 to PCR15 as a repair place with respect to PB 8IOunits A2112 to A2559. With this structure, Add_A Scan is only used withrespect to the EM NAND.

In exemplary embodiments, a manner of controlling the selection signalsYPCR and YCR is switched to one of the Pure NAND and the EM NAND basedon electrically stored product information (switching signal). Latchesfor defect bit information, comparison circuits and PB drivers shown inFIG. 43A are circuits that are used in a conventional Pure NAND product.In exemplary embodiments, it is possible to implement a switching meansof page buffer units (e.g., PB 8IO units CR0 to CR15 and PB 8IO unitsPCR0 to PCR15) of the Pure NAND and the EM NAND by adding a selectioncontrol on the selection signals YPCR and YCR. Also, as described above,since latches for defect bit information, comparison circuits and PBdrivers are reduced, an increase in chip size is suppressed andproductivity is improved.

While the inventive concept has been described with reference toexemplary embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the present invention. Therefore, it shouldbe understood that the above embodiments are not limiting, butillustrative.

What is claimed is:
 1. A semiconductor memory device comprising: a firstdata bus having a first width; a second data bus which is separate fromthe first data bus and which has a second width which is different fromthe first width; and a data transfer unit configured to operate in afirst operational mode for transferring data from memory cells and asecond operational mode for transferring data from the memory cells, thememory cells connected to a plurality of bit lines, wherein, in thefirst operational mode, the data transfer unit connects a first numberof bit lines from among the plurality of bit lines to the first data busto transfer the data, the first number being equal to the first width;and wherein, in the second operational mode, the data transfer unitconnects a second number of bit lines from among the plurality of bitlines to the second data bus to transfer the data, the second numberbeing equal to the second width.
 2. The semiconductor memory device ofclaim 1, wherein the first width is p and the second width is q, where pand q are natural numbers and p>q, and wherein the plurality of bitlines is n bit lines, where n is a natural number and a common multipleof p and q, wherein when (n/p) address signals are received, the datatransfer unit connects p bit lines to the first data bus in the firstoperational mode, and wherein when (n/q) address signals are received,the data transfer unit connects q bit lines to the second data bus inthe second operational mode.
 3. The semiconductor memory device of claim1, further comprising: a memory array; a page buffer which reads datafrom the memory array in a page unit and stores the read data; an ECCunit which corrects an error of the read data provided from the pagebuffer and writes the corrected data back in the page buffer; and aninterface unit which outputs the read data written back in the pagebuffer, and wherein the first data bus is connected to the ECC unit andthe second data bus is connected to the interface unit.
 4. Thesemiconductor memory device of claim 3, wherein the page buffer storeswrite data provided to the interface unit, and wherein the ECC unitgenerates parity data on the write data transferred from the page bufferand writes the parity data and the write data back in the page buffer.5. The semiconductor memory device of claim 3, wherein the memory arrayis a NAND flash memory cell array.
 6. A semiconductor memory devicecomprising: a first data bus having a first width; a second data buswhich is separate from the first data bus and which has a second widthwhich is different from the first width; and a data transfer unitconfigured to operate in a first operational mode for transferring datafrom memory cells and a second operational mode for transferring datafrom the memory cells, the memory cells connected to a plurality of bitlines, wherein, in the first operational mode, the data transfer unitconnects a first number of bit lines from among the plurality of bitlines to the first data bus to transfer the data, the first number beingequal to the first width; and wherein, in the second operational mode,the data transfer unit connects a second number of bit lines from amongthe plurality of bit lines to the second data bus to transfer the data,the second number being equal to the second width, wherein the datatransfer unit comprises: a first page buffer which amplifies a voltageof a bit line connected to a normal memory cell and latches theamplified result; a second page buffer which is replaced together with anormal memory cell and a bit line when a normal memory cell or a bitline connected to the first page buffer is defective; and a third pagebuffer which amplifies a voltage of a bit line connected to a paritymemory cell and latches the amplified result, wherein the second databus is connected to the first and second page buffers and the first databus is connected to the first to third page buffers.
 7. Thesemiconductor memory device of claim 6, further comprising: a fourthpage buffer which is connected to the first data bus and is replacedtogether with a parity memory cell and a bit line when a parity memorycell or a bit line connected to the first page buffer is defective; afirst repair circuit which is connected to the second data bus andreplaces a page buffer, associated with a defective memory cell or bitline, of the first page buffer with the second page buffer; a secondrepair circuit which is connected to the first data bus and replaces apage buffer, associated with a defective memory cell or bit line, of thethird page buffer with the fourth page buffer; and an ECC circuit whichis connected to the first data bus and corrects an error of data fromthe first and second page buffers based on data from the third andfourth page buffers.
 8. The semiconductor memory device of claim 7,further comprising: a page buffer control circuit which outputs fixeddata as an output of a page buffer, associated with a defective memorycell or bit line, of the first page buffer.
 9. The semiconductor memorydevice of claim 8, wherein the page buffer control circuit does notallow a write operation from the first data bus when a memory cell or abit line is defective.
 10. The semiconductor memory device of claim 7,wherein the first operational mode is a mode of operation in which inputdata of the ECC circuit is output as output data without repairing on apage buffer, associated with a defective memory cell or bit line, fromamong the first page buffer and the second page buffer used for a repairat the second operational mode.
 11. The semiconductor memory device ofclaim 6, wherein the first width is p and the second width is q, where pand q are natural numbers and p>q, and wherein the plurality of bitlines is n bit lines, where n is a natural number and a common multipleof p and q, wherein when (n/p) address signals are received, the datatransfer unit connects p bit lines to the first data bus in the firstoperational mode, and wherein when (n/q) address signals are received,the data transfer unit connects q bit lines to the second data bus inthe second operational mode.
 12. A semiconductor memory devicecomprising: a first data bus having a first width; a second data buswhich is separate from the first data bus and which has a second widthwhich is different from the first width; and a data transfer unitconfigured to operate in a first operational mode for transferring datafrom memory cells and a second operational mode for transferring datafrom the memory cells, the memory cells connected to a plurality of bitlines, wherein, in the first operational mode, the data transfer unitconnects a first number of bit lines from among the plurality of bitlines to the first data bus to transfer the data, the first number beingequal to the first width; and wherein, in the second operational mode,the data transfer unit connects a second number of bit lines from amongthe plurality of bit lines to the second data bus to transfer the data,the second number being equal to the second width, wherein the datatransfer unit comprises a first page buffer which latches data of a bitline connected to a normal memory cell; and a second page buffer whichlatches data of a bit line connected to a parity memory cell, whereinthe first data bus and the second data bus are connected to the firstpage buffer and the second page buffer, wherein the semiconductor memorydevice further comprises: an ECC circuit which is connected to the firstdata bus and corrects an error of output data of the first page bufferbased on output data of the second page buffer, wherein the firstoperational mode is a mode of operation in which the first page bufferis accessed and is also a mode of operation for execution of ECCprocessing where at a data write operation, the ECC circuit generatesparity data based on output data of the first page buffer and writes theparity data at the second page buffer and, at a data read operation, theECC circuit corrects an error of data of the first page buffer based onparity data of the second page buffer and writes the corrected data backin the first page buffer; wherein the second operational mode is a modeof operation in which the ECC processing is not executed and the secondpage buffer is not accessed and the first page buffer is accessed, andwherein selection and execution one of the first operational mode andthe second operational mode electrically switchable.
 13. Thesemiconductor memory device of claim 12, wherein the second page bufferis accessed through the second data bus at the second operational mode.14. The semiconductor memory device of claim 12, further comprising: amask circuit which outputs fixed data instead of data output to anexternal device through the second data bus when the second page bufferis accessed at the second operational mode.
 15. The semiconductor memorydevice of claim 12, further comprising: a third page buffer which isconnected to the first and second data buses and is replaced togetherwith a normal memory cell and a bit line when a normal memory cell or abit line connected to the first page buffer is defective; a fourth pagebuffer which is connected to the first and second data buses and isreplaced together with a parity memory cell and a bit line when a paritymemory cell or a bit line connected to the second page buffer isdefective; a first repair circuit which is connected to the second databus and replaces a page buffer, associated with a defective memory cellor bit line, of the first page buffer with the third page buffer at thesecond operational mode; and a second repair circuit which is connectedto the first data bus and replaces a page buffer, associated with adefective memory cell or bit line, of the second page buffer with thefourth page buffer.
 16. The semiconductor memory device of claim 15,wherein at the second operational mode, the first repair circuitreplaces a page buffer, associated with a defective memory cell or bitline, of the second page buffer with the fourth page buffer.
 17. Thesemiconductor memory device of claim 15, wherein the first repaircircuit stores a column address indicating a location of a page bufferto repair a page buffer, associated with a defective memory cell or bitline, of the first page buffer and selects a page buffer to be replacedby the stored column address; wherein the second repair circuit stores acolumn address indicating a location of a page buffer to repair a pagebuffer, associated with a defective memory cell or bit line, of thesecond page buffer and selects a page buffer to be replaced by thestored column address; and the semiconductor memory further comprising:a bit conversion circuit which converts a column address that the firstrepair circuit stores into a column address that the second repaircircuit stores.
 18. The semiconductor memory device of claim 17, whereinthe third page buffer and the fourth page buffer are selected by thefirst repair circuit and the second repair circuit, based on a switchingsignal indicating whether the semiconductor memory device operates ineither one of the first and second operational modes.
 19. Thesemiconductor memory device of claim 15, further comprising: a pagebuffer control circuit which outputs fixed data as an output of a pagebuffer, associated with a defective memory cell or bit line, from amongthe first to fourth page buffers, and wherein the page buffer controlcircuit does not allow a write operation from the first data bus when amemory cell or a bit line is defective.
 20. The semiconductor memorydevice of claim 12, wherein the first width is p and the second width isq, where p and q are natural numbers and p>q, and wherein the pluralityof bit lines is n bit lines, where n is a natural number and a commonmultiple of p and q, wherein when (n/p) address signals are received,the data transfer unit connects p bit lines to the first data bus in thefirst operational mode, and wherein when (n/q) address signals arereceived, the data transfer unit connects q bit lines to the second databus in the second operational mode.